ATmega168P Atmel Corporation, ATmega168P Datasheet
ATmega168P
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ATmega168P Summary of contents
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... Power-down Mode: 0.1µA – Power-save Mode: 0.8µA (Including 32kHz RTC) Note: 1. See ”Data Retention” on page 8 ® ® AVR 8-Bit Microcontroller ( compatible) for details. 8-bit Atmel Microcontroller with 4/8/16K Bytes In-System Programmable Flash ATmega48P/V ATmega88P/V ATmega168P/V Rev. 8025M–AVR–6/11 ...
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Pin Configurations Figure 1-1. Pinout ATmega48P/88P/168P TQFP Top View (PCINT19/OC2B/INT1) PD3 1 (PCINT20/XCK/T0) PD4 2 GND 3 VCC 4 GND 5 VCC 6 (PCINT6/XTAL1/TOSC1) PB6 7 (PCINT7/XTAL2/TOSC2) PB7 8 28 MLF Top View (PCINT19/OC2B/INT1) PD3 1 (PCINT20/XCK/T0) PD4 2 ...
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Pin Descriptions 1.1.1 VCC Digital supply voltage. 1.1.2 GND Ground. 1.1.3 Port B (PB7:0) XTAL1/XTAL2/TOSC1/TOSC2 Port 8-bit bi-directional I/O port with internal pull-up resistors (selected for each bit). The Port B output buffers have symmetrical drive ...
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The various special features of Port D are elaborated in 86. 1.1 the supply voltage pin for the A/D Converter, PC3:0, and ADC7:6. It should be externally CC connected to V through a low-pass filter. Note ...
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Block Diagram Figure 2-1. Block Diagram Watchdog Watchdog Oscillator Oscillator Circuits / Generation EEPROM 8bit T/C 0 8bit T/C 2 USART 0 PORT D (8) 8025M–AVR–6/11 Power Timer Supervision POR / BOD & RESET Flash Clock 16bit T/C 1 ...
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The AVR core combines a rich instruction set with 32 general purpose working registers. All the 32 registers are directly connected to the Arithmetic Logic Unit (ALU), allowing two independent registers to be accessed in one single instruction executed in ...
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... Comparison Between ATmega48P, ATmega88P and ATmega168P The ATmega48P, ATmega88P and ATmega168P differ only in memory sizes, boot loader sup- port, and interrupt vector sizes. sizes for the three devices. Table 2-1. Device ATmega48P ATmega88P ATmega168P ATmega88P and ATmega168P support a real Read-While-Write Self-Programming mechanism. ...
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Resources A comprehensive set of development tools, application notes and datasheets are available for download on http://www.atmel.com/avr. Note: 4. Data Retention Reliability Qualification results show that the projected data retention failure rate is much less than 1 PPM over ...
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AVR CPU Core 7.1 Overview This section discusses the AVR core architecture in general. The main function of the CPU core is to ensure correct program execution. The CPU must therefore be able to access memories, perform calculations, control ...
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ALU operation, two operands are output from the Register File, the operation is executed, and the result is stored back in the Register File – in one clock cycle. Six of the 32 registers can be used as three ...
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Instruction Set Reference. This will in many cases remove the need for using the dedicated compare instructions, resulting in faster and more compact code. The Status Register is not automatically stored when entering an interrupt routine and ...
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General Purpose Register File The Register File is optimized for the AVR Enhanced RISC instruction set. In order to achieve the required performance and flexibility, the following input/output schemes are supported by the Register File: • One 8-bit output ...
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The X-register, Y-register, and Z-register The registers R26..R31 have some added functions to their general purpose usage. These reg- isters are 16-bit address pointers for indirect addressing of the data space. The three indirect address registers X, Y, and ...
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SPH and SPL – Stack Pointer High and Stack Pointer Low Register Bit 0x3E (0x5E) 0x3D (0x5D) Read/Write Initial Value 7.6 Instruction Execution Timing This section describes the general access timing concepts for instruction execution. The AVR CPU is ...
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... The Reset Vector can also be moved to the start of the Boot Flash section by programming the BOOTRST Fuse, see ATmega88P and ATmega168P” on page When an interrupt occurs, the Global Interrupt Enable I-bit is cleared and all interrupts are dis- abled. The user software can write logic one to the I-bit to enable nested interrupts. All enabled interrupts can then interrupt the current interrupt routine. The I-bit is automatically set when a Return from Interrupt instruction – ...
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Assembly Code Example in r16, SREG cli sbi EECR, EEMPE sbi EECR, EEPE out SREG, r16 C Code Example char cSREG; cSREG = SREG; /* store SREG value */ /* disable interrupts during timed sequence */ _CLI(); EECR |= (1<<EEMPE); ...
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... For software security, the Flash Program memory space is divided into two sections, Boot Loader Section and Application Program Section in ATmega88P and ATmega168P. ATmega48P does not have separate Boot Loader and Application Program sec- tions, and the SPM instruction can be executed from the entire Flash. See SELFPRGEN ...
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... Figure 8-1. Figure 8-2. ATmega48P/88P/168P 18 Program Memory Map, ATmega48P Program Memory Application Flash Section Program Memory Map, ATmega88P and ATmega168P Program Memory Application Flash Section Boot Flash Section 0x0000 0x7FF 0x0000 0x0FFF/0x1FFF 8025M–AVR–6/11 ...
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SRAM Data Memory Figure 8-3 The ATmega48P/88P/168P is a complex microcontroller with more peripheral units than can be supported within the 64 locations reserved in the Opcode for the IN and OUT instructions. For the Extended I/O space from ...
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Data Memory Access Times This section describes the general access timing concepts for internal memory access. The internal data SRAM access is performed in two clk Figure 8-4. 8.4 EEPROM Data Memory The ATmega48P/88P/168P contains 256/512/512 bytes of data ...
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Preventing EEPROM Corruption During periods of low V too low for the CPU and the EEPROM to operate properly. These issues are the same as for board level systems using EEPROM, and the same design solutions should be applied. ...
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Register Description 8.6.1 EEARH and EEARL – The EEPROM Address Register Bit 0x22 (0x42) 0x21 (0x41) Read/Write Initial Value • Bits 15:9 – Reserved These bits are reserved bits in the ATmega48P/88P/168P and will always read as zero. • ...
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... Step 2 is only relevant if the software contains a Boot Loader allowing the CPU to program the Flash. If the Flash is never being updated by the CPU, step 2 can be omitted. See Support – Read-While-Write Self-Programming, ATmega88P and ATmega168P” on page 275 for details about Boot programming. ...
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When the write access time has elapsed, the EEPE bit is cleared by hardware. The user soft- ware can poll this bit and wait for a zero before writing the next byte. When EEPE has been set, the CPU is ...
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Assembly Code Example EEPROM_write: C Code Example void EEPROM_write(unsigned int uiAddress, unsigned char ucData 8025M–AVR–6/11 ; Wait for completion of previous write sbic EECR,EEPE rjmp EEPROM_write ; Set up address (r18:r17) in address register out EEARH, r18 out ...
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The next code examples show assembly and C functions for reading the EEPROM. The exam- ples assume that interrupts are controlled so that no interrupts will occur during execution of these functions. Assembly Code Example EEPROM_read: ; Wait for completion ...
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System Clock and Clock Options 9.1 Clock Systems and their Distribution Figure 9-1 need not be active at a given time. In order to reduce power consumption, the clocks to modules not being used can be halted by using ...
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Asynchronous Timer Clock – clk The Asynchronous Timer clock allows the Asynchronous Timer/Counter to be clocked directly from an external clock or an external 32 kHz clock crystal. The dedicated clock domain allows using this Timer/Counter as a real-time ...
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Table 9-2. Typ Time-out (V Main purpose of the delay is to keep the AVR in reset until it is supplied with minimum V delay will not monitor the actual voltage ...
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Figure 9-2. The Low Power Oscillator can operate in three different modes, each optimized for a specific fre- quency range. The operating mode is selected by the fuses CKSEL[3:1] as shown in on page Table 9-3. Frequency Range Notes: The ...
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Table 9-4. Oscillator Source / Power Conditions Crystal Oscillator, BOD enabled Crystal Oscillator, fast rising power Crystal Oscillator, slowly rising power Notes: 9.4 Full Swing Crystal Oscillator Pins XTAL1 and XTAL2 are input and output, respectively inverting amplifier ...
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Figure 9-3. Table 9-6. Oscillator Source / Power Conditions Ceramic resonator, fast rising power Ceramic resonator, slowly rising power Ceramic resonator, BOD enabled Ceramic resonator, fast rising power Ceramic resonator, slowly rising power Crystal Oscillator, BOD enabled Crystal Oscillator, fast ...
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Low Frequency Crystal Oscillator The Low-frequency Crystal Oscillator is optimized for use with a 32.768 kHz watch crystal. When selecting crystals, load capasitance and crystal’s Equivalent Series Resistance, ESR must be taken into consideration. Both values are specified by ...
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Table 9-10. CKSEL[3:0] 0100 0101 Note: 9.6 Calibrated Internal RC Oscillator By default, the Internal RC Oscillator provides an approximate 8.0 MHz clock. Though voltage and temperature dependent, this clock can be very accurately calibrated by the user. See 29-1 ...
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Internal Oscillator The 128 kHz internal Oscillator is a low power Oscillator providing a clock of 128 kHz. The fre- quency is nominal at 3V and 25°C. This clock may be select as the system clock by ...
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Table 9-16. Power Conditions BOD enabled Fast rising power Slowly rising power When applying an external clock required to avoid sudden changes in the applied clock fre- quency to ensure stable operation of the MCU. A variation in ...
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The ripple counter that implements the prescaler runs at the frequency of the undivided clock, which may be faster than the ...
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Register Description 9.12.1 OSCCAL – Oscillator Calibration Register Bit (0x66) Read/Write Initial Value • Bits 7:0 – CAL[7:0]: Oscillator Calibration Value The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to remove process variations from ...
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The CKDIV8 Fuse determines the initial value of the CLKPS bits. If CKDIV8 is unprogrammed, the CLKPS bits will be reset to “0000”. If CKDIV8 is programmed, CLKPS bits are reset to “0011”, giving a division factor ...
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Power Management and Sleep Modes Sleep modes enable the application to shut down unused modules in the MCU, thereby saving power. The AVR provides various sleep modes allowing the user to tailor the power consump- tion to the application’s ...
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BOD Disable When the Brown-out Detector (BOD) is enabled by BODLEVEL fuses, the BOD is actively monitoring the power supply voltage during a sleep period. To save power possible to disable the BOD by software for some ...
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Power-down Mode When the SM[2:0] bits are written to 010, the SLEEP instruction makes the MCU enter Power- down mode. In this mode, the external Oscillator is stopped, while the external interrupts, the 2- wire Serial Interface address watch, ...
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Power Reduction Register The Power Reduction Register (PRR), see vides a method to stop the clock to individual peripherals to reduce power consumption. The current state of the peripheral is frozen and the I/O registers can not be read ...
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Watchdog Timer If the Watchdog Timer is not needed in the application, the module should be turned off. If the Watchdog Timer is enabled, it will be enabled in all sleep modes and hence always consume power. In the ...
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Register Description 10.11.1 SMCR – Sleep Mode Control Register The Sleep Mode Control Register contains control bits for power management. Bit 0x33 (0x53) Read/Write Initial Value • Bits 7:4 – Reserved These bits are unused bits in the ATmega48P/88P/168P, ...
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Then, to set the BODS bit, BODS must be set to one and BODSE must be set to zero within four clock cycles. The BODS bit is active three clock cycles after it is set. A ...
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... During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset Vector. For the ATmega168P, the instruction placed at the Reset Vector must be a JMP – Absolute Jump – instruction to the reset handling routine. For the ATmega48P and ATmega88P, the instruction placed at the Reset Vector must be an RJMP – ...
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Figure 11-1. Reset Logic BODLEVEL [2..0] RSTDISBL 11.3 Power-on Reset A Power-on Reset (POR) pulse is generated by an On-chip detection circuit. The detection level is defined below the detection level. The POR circuit can be used ...
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Figure 11-3. MCU Start-up, RESET Extended Externally TIME-OUT INTERNAL 11.4 External Reset An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the minimum pulse width (see reset, even if the clock is ...
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Figure 11-5. Brown-out Reset During Operation 11.6 Watchdog System Reset When the Watchdog times out, it will generate a short reset pulse of one CK cycle duration. On the falling edge of this pulse, the delay timer starts counting the ...
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ADC is used. To reduce power consumption in Power-down mode, the user can avoid the three conditions above to ensure that the reference is turned off before entering Power-down mode. 11.8 Watchdog Timer 11.8.1 Features • Clocked from separate On-chip ...
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To further ensure program security, altera- tions to the Watchdog set-up must follow timed sequences. The sequence for clearing WDE and changing time-out configuration is as follows the ...
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Assembly Code Example WDT_off: C Code Example void WDT_off(void Note: Note: If the Watchdog is accidentally enabled, for example by a runaway pointer or brown-out condition, the device will be reset and the Watchdog Timer will stay enabled. ...
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The following code example shows one assembly and one C function for changing the time-out value of the Watchdog Timer. Assembly Code Example WDT_Prescaler_Change: ; Turn off global interrupt cli ; Reset Watchdog Timer wdr ; Start timed sequence lds ...
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Register Description 11.9.1 MCUSR – MCU Status Register The MCU Status Register provides information on which reset source caused an MCU reset. Bit 0x35 (0x55) Read/Write Initial Value • Bit 7:4 – Reserved These bits are unused bits in ...
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WDIF automatically by hardware (the Watchdog goes to System Reset Mode). This is useful for keeping the Watchdog Timer security while using the interrupt. To stay in Interrupt and System Reset Mode, WDIE must be set after each interrupt. This ...
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Table 11-2. WDP3 8025M–AVR–6/11 Watchdog Timer Prescale Select (Continued) Number of WDT Oscillator WDP2 WDP1 WDP0 512K (524288) cycles 1024K (1048576) cycles ...
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... Each Interrupt Vector occupies two instruction words in ATmega168P, and one instruction word in ATmega48P and ATmega88P. • ATmega48P does not have a separate Boot Loader Section. In ATmega88P and ATmega168P, the Reset Vector is affected by the BOOTRST fuse, and the Interrupt Vector start address is affected by the IVSEL bit in MCUCR. 12.1 Interrupt Vectors in ATmega48P Table 12-1 ...
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Table 12-1. Reset and Interrupt Vectors in ATmega48P (Continued) Vector No. Program Address 24 0x017 25 0x018 26 0x019 The most typical and general program setup for the Reset and Interrupt Vector Addresses in ATmega48P is: Address Labels Code 0x000 ...
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... When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at reset, see port – Read-While-Write Self-Programming, ATmega88P and ATmega168P” on page 2. When the IVSEL bit in MCUCR is set, Interrupt Vectors will be moved to the start of the Boot Flash Section. The address of each Interrupt Vector will then be the address in this table added to the start address of the Boot Flash Section ...
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Table 12-3. BOOTRST Note: The most typical and general program setup for the Reset and Interrupt Vector Addresses in ATmega88P is: Address Labels Code 0x000 0x001 0x002 0x003 0x004 0x005 0x006 0x007 0X008 0x009 0x00A 0x00B 0x00C 0x00D 0x00E 0x00F ...
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When the BOOTRST Fuse is unprogrammed, the Boot section size set to 2K bytes and the IVSEL bit in the MCUCR Register is set before any interrupts are enabled, the most typical and general program setup for the Reset and ...
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... When the BOOTRST Fuse is programmed, the device will jump to the Boot Loader address at reset, see port – Read-While-Write Self-Programming, ATmega88P and ATmega168P” on page 2. When the IVSEL bit in MCUCR is set, Interrupt Vectors will be moved to the start of the Boot Flash Section. The address of each Interrupt Vector will then be the address in this table added to the start address of the Boot Flash Section. 8025M– ...
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... ATmega48P/88P/168P 64 shows reset and Interrupt Vectors placement for the various combina- Reset and Interrupt Vectors Placement in ATmega168P IVSEL Reset Address 0 0x000 1 0x000 0 Boot Reset Address 1 Boot Reset Address 1. The Boot Reset Address is shown in means unprogrammed while “ ...
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... When the BOOTRST Fuse is unprogrammed, the Boot section size set to 2K bytes and the IVSEL bit in the MCUCR Register is set before any interrupts are enabled, the most typical and general program setup for the Reset and Interrupt Vector Addresses in ATmega168P is: Address Labels Code ...
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... Register Description 12.4.1 Moving Interrupts Between Application and Boot Space, ATmega88P and ATmega168P The MCU Control Register controls the placement of the Interrupt Vector table. 12.4.2 MCUCR – MCU Control Register Bit 0x35 (0x55) Read/Write Initial Value • Bit 1 – IVSEL: Interrupt Vector Select When the IVSEL bit is cleared (zero), the Interrupt Vectors are placed at the start of the Flash memory ...
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Bit 0 – IVCE: Interrupt Vector Change Enable The IVCE bit must be written to logic one to enable change of the IVSEL bit. IVCE is cleared by hardware four cycles after it is written or when IVSEL is ...
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External Interrupts The External Interrupts are triggered by the INT0 and INT1 pins or any of the PCINT[23:0] pins. Observe that, if enabled, the interrupts will trigger even if the INT0 and INT1 or PCINT[23:0] pins are configured as ...
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Register Description 13.2.1 EICRA – External Interrupt Control Register A The External Interrupt Control Register A contains control bits for interrupt sense control. Bit (0x69) Read/Write Initial Value • Bit 7:4 – Reserved These bits are unused bits in ...
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EIMSK – External Interrupt Mask Register Bit 0x1D (0x3D) Read/Write Initial Value • Bit 7:2 – Reserved These bits are unused bits in the ATmega48P/88P/168P, and will always read as zero. • Bit 1 – INT1: External Interrupt Request ...
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PCICR – Pin Change Interrupt Control Register Bit (0x68) Read/Write Initial Value • Bit 7:3 – Reserved These bits are unused bits in the ATmega48P/88P/168P, and will always read as zero. • Bit 2 – PCIE2: Pin Change Interrupt ...
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Bit 0 – PCIF0: Pin Change Interrupt Flag 0 When a logic change on any PCINT[7:0] pin triggers an interrupt request, PCIF0 becomes set (one). If the I-bit in SREG and the PCIE0 bit in PCICR are set (one), ...
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I/O-Ports 14.1 Overview All AVR ports have true Read-Modify-Write functionality when used as general digital I/O ports. This means that the direction of one port pin can be changed without unintentionally changing the direction of any other pin with ...
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Note that enabling the alternate function of some of the port pins does not affect the use of the other pins in the port as general digital I/O. 14.2 Ports as General Digital I/O The ports are bi-directional I/O ports ...
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If PORTxn is written logic one when the pin is configured as an output pin, the port pin is driven high (one). If PORTxn is written logic zero when the pin is configured as an output pin, the port pin ...
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Figure 14-3. Synchronization when Reading an Externally Applied Pin value INSTRUCTIONS Consider the clock period starting shortly after the first falling edge of the system clock. The latch is closed when the clock is low, and goes transparent when the ...
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Assembly Code Example C Code Example unsigned char i; Note: 14.2.5 Digital Input Enable and Sleep Modes As shown in Schmitt Trigger. The signal denoted SLEEP in the figure, is set by the MCU Sleep Controller in Power-down mode, Power-save ...
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Active mode and Idle mode). The simplest method to ensure a defined level of an unused pin enable ...
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Table 14-2 ure 14-5 on page 78 generated internally in the modules having the alternate function. Table 14-2. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV PTOE DIEOE DIEOV DI AIO The following subsections shortly describe the alternate functions for ...
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Alternate Functions of Port B The Port B pins with alternate functions are shown in Table 14-3. Port Pin PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0 The alternate pin configuration is as follows: • XTAL2/TOSC2/PCINT7 – Port B, ...
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AS2 bit in ASSR is set (one) to enable asynchronous clocking of Timer/Counter2, pin PB6 is dis- connected from the port, and becomes the input of the inverting Oscillator amplifier. In this mode, a crystal Oscillator is connected to this ...
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The OC1A pin is also the output pin for the PWM mode timer function. PCINT1: Pin Change Interrupt source 1. The PB1 pin can serve as an external interrupt source. • ICP1/CLKO/PCINT0 – Port B, ...
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Table 14-5. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO 14.3.2 Alternate Functions of Port C The Port C pins with alternate functions are shown in Table 14-6. Port Pin 8025M–AVR–6/11 Overriding Signals for Alternate Functions ...
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The alternate pin configuration is as follows: • RESET/PCINT14 – Port C, Bit 6 RESET, Reset pin: When the RSTDISBL Fuse is programmed, this pin functions as a normal I/O pin, and the part will have to rely on Power-on ...
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ADC1/PCINT9 – Port C, Bit 1 PC1 can also be used as ADC input Channel 1. Note that ADC input channel 1 uses analog power. PCINT9: Pin Change Interrupt source 9. The PC1 pin can serve as an external ...
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Table 14-8. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO 14.3.3 Alternate Functions of Port D The Port D pins with alternate functions are shown in Table 14-9. Port Pin PD7 PD6 PD5 PD4 PD3 PD2 ...
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The alternate pin configuration is as follows: • AIN1/OC2B/PCINT23 – Port D, Bit 7 AIN1, Analog Comparator Negative Input. Configure the port pin as input with the internal pull-up switched off to avoid the digital port function from interfering with ...
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INT0/PCINT18 – Port D, Bit 2 INT0, External Interrupt source 0: The PD2 pin can serve as an external interrupt source. PCINT18: Pin Change Interrupt source 18. The PD2 pin can serve as an external interrupt source. • TXD/PCINT17 ...
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Table 14-11. Overriding Signals for Alternate Functions in PD3..PD0 Signal Name PUOE PUO DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO 8025M–AVR–6/11 PD3/OC2B/INT1/ PD2/INT0/ PCINT19 PCINT18 OC2B ENABLE 0 OC2B 0 INT1 ...
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Register Description 14.4.1 MCUCR – MCU Control Register Bit 0x35 (0x55) Read/Write Initial Value • Bit 4 – PUD: Pull-up Disable When this bit is written to one, the pull-ups in the I/O ports are disabled even if the ...
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PORTD – The Port D Data Register Bit 0x0B (0x2B) Read/Write Initial Value 14.4.9 DDRD – The Port D Data Direction Register Bit 0x0A (0x2A) Read/Write Initial Value 14.4.10 PIND – The Port D Input Pins Address Bit 0x09 ...
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Timer/Counter0 with PWM 15.1 Features • Two Independent Output Compare Units • Double Buffered Output Compare Registers • Clear Timer on Compare Match (Auto Reload) • Glitch Free, Phase Correct Pulse Width Modulator (PWM) • Variable PWM Period ...
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Figure 15-1. 8-bit Timer/Counter Block Diagram 15.2.1 Definitions Many register and bit references in this section are written in general form. A lower case “n” replaces the Timer/Counter number, in this case 0. A lower case “x” replaces the Output ...
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The Timer/Counter can be clocked internally, via the prescaler external clock source on the T0 pin. The Clock Select logic block controls which clock source and edge the Timer/Counter uses to increment (or decrement) its value. The ...
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The counting sequence is determined by the setting of the WGM01 and WGM00 bits located in the Timer/Counter Control Register (TCCR0A) and the WGM02 bit located in the Timer/Counter Control Register B (TCCR0B). There are close connections between how the ...
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The OCR0x Register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCR0x Buffer Register, and if double buffering is dis- abled the CPU will access the OCR0x ...
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Figure 15-4. Compare Match Output Unit, Schematic The general I/O port function is overridden by the Output Compare (OC0x) from the Waveform Generator if either of the COM0x1:0 bits are set. However, the OC0x pin direction (input or out- put) ...
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Normal Mode The simplest mode of operation is the Normal mode (WGM02:0 = 0). In this mode the counting direction is always up (incrementing), and no counter clear is performed. The counter simply overruns when it passes its maximum ...
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The waveform generated will have a maximum frequency when OCR0A is set to zero (0x00). The waveform frequency is defined by the following clk_I/O equation: The N variable represents the ...
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In fast PWM mode, the compare unit allows generation of PWM waveforms on the OC0x pins. Setting the COM0x1:0 bits to two will produce a non-inverted PWM and an inverted PWM output can be generated by setting the COM0x1:0 to ...
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Figure 15-7. Phase Correct PWM Mode, Timing Diagram TCNTn OCnx OCnx Period The Timer/Counter Overflow Flag (TOV0) is set each time the counter reaches BOTTOM. The Interrupt Flag can be used to generate an interrupt each time the counter reaches ...
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BOTTOM the OCnx value at MAX must correspond to the result of an up- counting Compare Match. • The timer starts counting from a value higher than the one in OCRnx, and for that reason misses the Compare ...
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Figure 15-10. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (f clk clk (clk TCNTn OCRnx OCFnx Figure 15-11 PWM mode where OCR0A is TOP. Figure 15-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres- clk clk ...
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Register Description 15.9.1 TCCR0A – Timer/Counter Control Register A Bit 0x24 (0x44) Read/Write Initial Value • Bits 7:6 – COM0A[1:0]: Compare Match Output A Mode These bits control the Output Compare pin (OC0A) behavior. If one or both of ...
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Table 15-4 rect PWM mode. Table 15-4. COM0A1 Note: • Bits 5:4 – COM0B1:0: Compare Match Output B Mode These bits control the Output Compare pin (OC0B) behavior. If one or both of the COM0B1:0 bits ...
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Table 15-7 rect PWM mode. Table 15-7. COM0B1 Note: • Bits 3, 2 – Reserved These bits are reserved bits in the ATmega48P/88P/168P and will always read as zero. • Bits 1:0 – WGM01:0: Waveform Generation ...
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TCCR0B – Timer/Counter Control Register B Bit 0x25 (0x45) Read/Write Initial Value • Bit 7 – FOC0A: Force Output Compare A The FOC0A bit is only active when the WGM bits specify a non-PWM mode. However, for ensuring compatibility ...
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Table 15-9. CS02 external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter even if the pin is configured as an output. This feature ...
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TIMSK0 – Timer/Counter Interrupt Mask Register Bit (0x6E) Read/Write Initial Value • Bits 7:3 – Reserved These bits are reserved bits in the ATmega48P/88P/168P and will always read as zero. • Bit 2 – OCIE0B: Timer/Counter Output Compare Match ...
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Bit 0 – TOV0: Timer/Counter0 Overflow Flag The bit TOV0 is set when an overflow occurs in Timer/Counter0. TOV0 is cleared by hardware when executing the corresponding interrupt handling vector. Alternatively, TOV0 is cleared by writing a logic one ...
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Timer/Counter1 with PWM 16.1 Features • True 16-bit Design (i.e., Allows 16-bit PWM) • Two independent Output Compare Units • Double Buffered Output Compare Registers • One Input Capture Unit • Input Capture Noise Canceler • Clear Timer ...
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Figure 16-1. 16-bit Timer/Counter Block Diagram Note: 16.2.1 Registers The Timer/Counter (TCNT1), Output Compare Registers (OCR1A/B), and Input Capture Regis- ter (ICR1) are all 16-bit registers. Special procedures must be followed when accessing the 16- bit registers. These procedures are ...
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Compare Units” on page Flag (OCF1A/B) which can be used to generate an Output Compare interrupt request. The Input Capture Register can capture the Timer/Counter value at a given external (edge trig- gered) event on either the Input Capture ...
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Assembly Code Examples ... ; Set TCNT1 to 0x01FF ldi r17,0x01 ldi r16,0xFF out TCNT1H,r17 out TCNT1L,r16 ; Read TCNT1 into r17:r16 in r16,TCNT1L in r17,TCNT1H ... C Code Examples unsigned int i; ... /* Set TCNT1 to 0x01FF */ ...
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Assembly Code Example TIM16_ReadTCNT1: C Code Example unsigned int TIM16_ReadTCNT1( void ) { } Note: The assembly code example returns the TCNT1 value in the r17:r16 register pair. The following code examples show how atomic write of ...
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Assembly Code Example TIM16_WriteTCNT1: ; Save global interrupt flag in r18,SREG ; Disable interrupts cli ; Set TCNT1 to r17:r16 out TCNT1H,r17 out TCNT1L,r16 ; Restore global interrupt flag out SREG,r18 ret C Code Example void TIM16_WriteTCNT1( unsigned int i ...
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Counter Unit The main part of the 16-bit Timer/Counter is the programmable 16-bit bi-directional counter unit. Figure 16-2 Figure 16-2. Counter Unit Block Diagram Signal description (internal signals): Count Direction Clear clk TOP BOTTOM The 16-bit counter is mapped ...
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The Timer/Counter Overflow Flag (TOV1) is set according to the mode of operation selected by the WGM13:0 bits. TOV1 can be used for generating a CPU interrupt. 16.6 Input Capture Unit The Timer/Counter incorporates an Input Capture unit that can ...
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TOP value can be written to the ICR1 Register. When writing the ICR1 Register the high byte must be written to the ICR1H I/O location before the low byte is written ...
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I/O bit location). For measuring frequency only, the clearing of the ICF1 Flag is not required (if an interrupt handler is used). 16.7 Output Compare Units The 16-bit comparator continuously compares ...
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PWM pulses, thereby making the out- put glitch-free. The OCR1x Register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCR1x Buffer ...
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Compare Match Output Unit The Compare Output mode (COM1x1:0) bits have two functions. The Waveform Generator uses the COM1x1:0 bits for defining the Output Compare (OC1x) state at the next compare match. Secondly the COM1x1:0 bits control the OC1x ...
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PWM refer to page 133. A change of the COM1x1:0 bits state will have effect at the first compare match after the bits are written. ...
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Figure 16-6. CTC Mode, Timing Diagram TCNTn OCnA (Toggle) Period An interrupt can be generated at each time the counter value reaches the TOP value by either using the OCF1A or ICF1 Flag according to the register used to define ...
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The PWM resolution for fast PWM can be fixed to 8-, 9-, or 10-bit, or defined by either ICR1 or OCR1A. The minimum resolution allowed is 2-bit (ICR1 or OCR1A set to 0x0003), and the max- imum resolution is 16-bit ...
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When the OCR1A I/O location is written the value written will be put into the OCR1A Buffer Register. The OCR1A Compare Register will then be updated with the value in the Buffer Register at the next ...
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OCR1A set to MAX). The PWM resolu- tion in bits can be calculated by using the following equation: In phase correct PWM mode the counter is incremented until the counter value ...
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TOP value, while the length of the rising slope is determined by the new TOP value. When these two values differ the two slopes of the period ...
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OCR1A set to MAX). The PWM resolution in bits can be calculated using the following equation: In phase and frequency correct PWM mode the counter is incremented until the counter value matches either ...
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Using the ICR1 Register for defining TOP works well when using fixed TOP values. By using ICR1, the OCR1A Register is free to be used for generating a PWM output on OC1A. However, if the base PWM frequency is actively ...
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Figure 16-11. Timer/Counter Timing Diagram, Setting of OCF1x, with Prescaler (f Figure 16-12 frequency correct PWM mode the OCR1x Register is updated at BOTTOM. The timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by ...
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Figure 16-13 Figure 16-13. Timer/Counter Timing Diagram, with Prescaler (f and ICF n 16.11 Register Description 16.11.1 TCCR1A – Timer/Counter1 Control Register A Bit (0x80) Read/Write Initial Value • Bit 7:6 – COM1A1:0: Compare Output Mode for Channel A • ...
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Table 16-2 PWM mode. Table 16-2. COM1A1/COM1B1 Note: Table 16-3 correct or the phase and frequency correct, PWM mode. Table 16-3. COM1A1/COM1B1 Note: • Bit 1:0 – WGM11:0: Waveform Generation Mode Combined with the WGM13:2 bits found in the TCCR1B ...
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Table 16-4. Waveform Generation Mode Bit Description WGM12 WGM11 Mode WGM13 (CTC1) (PWM11 ...
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When the ICR1 is used as TOP value (see description of the WGM13:0 bits located in the TCCR1A and the TCCR1B Register), the ICP1 is disconnected and consequently the Input Cap- ture function is disabled. • Bit 5 – Reserved ...
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TCNT1H and TCNT1L – Timer/Counter1 Bit (0x85) (0x84) Read/Write Initial Value The two Timer/Counter I/O locations (TCNT1H and TCNT1L, combined TCNT1) give direct access, both for read and for write operations, to the Timer/Counter unit 16-bit counter. To ensure ...
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ICR1H and ICR1L – Input Capture Register 1 Bit (0x87) (0x86) Read/Write Initial Value The Input Capture is updated with the counter (TCNT1) value each time an event occurs on the ICP1 pin (or optionally on the Analog Comparator ...
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TIFR1 – Timer/Counter1 Interrupt Flag Register Bit 0x16 (0x36) Read/Write Initial Value • Bit 7, 6 – Reserved These bits are unused bits in the ATmega48P/88P/168P, and will always read as zero. • Bit 5 – ICF1: Timer/Counter1, Input ...
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Timer/Counter0 and Timer/Counter1 Prescalers ”8-bit Timer/Counter0 with PWM” on page 92 111 share the same prescaler module, but the Timer/Counters can have different prescaler set- tings. The description below applies to both Timer/Counter1 and Timer/Counter0. 17.1 Internal Clock Source ...
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Enabling and disabling of the clock input must be done when T1/T0 has been stable for at least one system clock cycle, otherwise risk that a false Timer/Counter clock pulse is generated. Each half period of the ...
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Register Description 17.4.1 GTCCR – General Timer/Counter Control Register Bit 0x23 (0x43) Read/Write Initial Value • Bit 7 – TSM: Timer/Counter Synchronization Mode Writing the TSM bit to one activates the Timer/Counter Synchronization mode. In this mode, the value ...
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Timer/Counter2 with PWM and Asynchronous Operation 18.1 Features • Single Channel Counter • Clear Timer on Compare Match (Auto Reload) • Glitch-free, Phase Correct Pulse Width Modulator (PWM) • Frequency Generator • 10-bit Clock Prescaler • Overflow and ...
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Registers The Timer/Counter (TCNT2) and Output Compare Register (OCR2A and OCR2B) are 8-bit reg- isters. Interrupt request (shorten as Int.Req.) signals are all visible in the Timer Interrupt Flag Register (TIFR2). All interrupts are individually masked with the Timer ...
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Figure 18-2. Counter Unit Block Diagram Signal description (internal signals): count direction clear clk top bottom Depending on the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clk selected by the Clock Select ...
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Figure 18-3. Output Compare Unit, Block Diagram The OCR2x Register is double buffered when using any of the Pulse Width Modulation (PWM) modes. For the Normal and Clear Timer on Compare (CTC) modes of operation, the double buffering is disabled. ...
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The setup of the OC2x should be performed before setting the Data Direction Register for the port pin to output. The easiest way of setting the OC2x value is to use the Force Output Com- pare (FOC2x) strobe bit in ...
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Compare Output Mode and Waveform Generation The Waveform Generator uses the COM2x1:0 bits differently in normal, CTC, and PWM modes. For all modes, setting the COM2x1 tells the Waveform Generator that no action on the OC2x Register ...
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Figure 18-5. CTC Mode, Timing Diagram TCNTn OCnx (Toggle) Period An interrupt can be generated each time the counter value reaches the TOP value by using the OCF2A Flag. If the interrupt is enabled, the interrupt handler routine can be ...
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In fast PWM mode, the counter is incremented until the counter value matches the TOP value. The counter is then cleared at the following timer clock cycle. The timing diagram for the fast PWM mode is shown in togram for ...
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OC2A toggle in CTC mode, except the double buffer feature of the Output Compare unit is enabled in the fast PWM mode. 18.7.4 Phase Correct PWM Mode ...
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COM2x1:0 to three. TOP is defined as 0xFF when WGM2 and OCR2A when MGM2 (See value will only be visible on the port pin if the data direction for ...
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Figure 18-9. Timer/Counter Timing Diagram, with Prescaler (f clk clk (clk TCNTn TOVn Figure 18-10 Figure 18-10. Timer/Counter Timing Diagram, Setting of OCF2A, with Prescaler (f clk clk (clk TCNTn OCRnx OCFnx Figure 18-11 Figure 18-11. Timer/Counter Timing Diagram, Clear ...
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Asynchronous Operation of Timer/Counter2 When Timer/Counter2 operates asynchronously, some considerations must be taken. • Warning: When switching between asynchronous and synchronous clocking of Timer/Counter2, the Timer Registers TCNT2, OCR2x, and TCCR2x might be corrupted. A safe procedure for switching ...
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Description of wake up from Power-save or ADC Noise Reduction mode when the timer is clocked asynchronously: When the interrupt condition is met, the wake up process is started on the following cycle of the timer clock, that is, ...
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When AS2 is set, pins TOSC1 and TOSC2 are disconnected from Port C. A crystal can then be connected between the TOSC1 and TOSC2 pins to serve as an independent clock source for Timer/Counter2. The Oscillator is optimized for ...
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Register Description 18.11.1 TCCR2A – Timer/Counter Control Register A Bit (0xB0) Read/Write Initial Value • Bits 7:6 – COM2A1:0: Compare Match Output A Mode These bits control the Output Compare pin (OC2A) behavior. If one or both of the ...
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Table 18-4 rect PWM mode. Table 18-4. COM2A1 Note: • Bits 5:4 – COM2B1:0: Compare Match Output B Mode These bits control the Output Compare pin (OC2B) behavior. If one or both of the COM2B1:0 bits ...
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Note: Table 18-7 rect PWM mode. Table 18-7. COM2B1 Note: • Bits 3, 2 – Reserved These bits are reserved bits in the ATmega48P/88P/168P and will always read as zero. • Bits 1:0 – WGM21:0: Waveform ...
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TCCR2B – Timer/Counter Control Register B Bit (0xB1) Read/Write Initial Value • Bit 7 – FOC2A: Force Output Compare A The FOC2A bit is only active when the WGM bits specify a non-PWM mode. However, for ensuring compatibility with ...
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Table 18-9. CS22 external pin modes are used for the Timer/Counter0, transitions on the T0 pin will clock the counter even if the pin is configured as an output. This feature ...
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TIMSK2 – Timer/Counter2 Interrupt Mask Register Bit (0x70) Read/Write Initial Value • Bit 2 – OCIE2B: Timer/Counter2 Output Compare Match B Interrupt Enable When the OCIE2B bit is written to one and the I-bit in the Status Register is ...
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ASSR – Asynchronous Status Register Bit (0xB6) Read/Write Initial Value • Bit 7 – RES: Reserved bit This bit is reserved and will always read as zero. • Bit 6 – EXCLK: Enable External Clock Input When EXCLK is ...
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The mechanisms for reading TCNT2, OCR2A, OCR2B, TCCR2A and TCCR2B are different. When reading TCNT2, the actual timer value is read. When reading OCR2A, OCR2B, TCCR2A and TCCR2B the value in the temporary storage register is read. 18.11.9 GTCCR – ...
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SPI – Serial Peripheral Interface 19.1 Features • Full-duplex, Three-wire Synchronous Data Transfer • Master or Slave Operation • LSB First or MSB First Data Transfer • Seven Programmable Bit Rates • End of Transmission Interrupt Flag • Write ...
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The interconnection between Master and Slave CPUs with SPI is shown in 165. The system consists of two shift Registers, and a Master clock generator. The SPI Master initiates the communication cycle when pulling low the Slave Select SS pin ...
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When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is overridden according to ”Alternate Port Functions” on page Table 19-1. Pin MOSI MISO SCK SS Note: The following code examples show how to ...
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Assembly Code Example SPI_MasterInit: SPI_MasterTransmit: Wait_Transmit: C Code Example void SPI_MasterInit(void void SPI_MasterTransmit(char cData Note: 8025M–AVR–6/11 (1) ; Set MOSI and SCK output, all others input ldi r17,(1<<DD_MOSI)|(1<<DD_SCK) out DDR_SPI,r17 ; Enable SPI, Master, set clock ...
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The following code examples show how to initialize the SPI as a Slave and how to perform a simple reception. Assembly Code Example SPI_SlaveInit: ; Set MISO output, all others input ldi out ; Enable SPI ldi out ret SPI_SlaveReceive: ...
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SS Pin Functionality 19.3.1 Slave Mode When the SPI is configured as a Slave, the Slave Select (SS) pin is always input. When SS is held low, the SPI is activated, and MISO becomes an output if configured so ...
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Figure 19-3. SPI Transfer Format with CPHA = 0 Figure 19-4. SPI Transfer Format with CPHA = 1 ATmega48P/88P/168P 170 SCK (CPOL = 0) mode 0 SCK (CPOL = 1) mode 2 SAMPLE I MOSI/MISO CHANGE 0 MOSI PIN CHANGE ...
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Register Description 19.5.1 SPCR – SPI Control Register Bit 0x2C (0x4C) Read/Write Initial Value • Bit 7 – SPIE: SPI Interrupt Enable This bit causes the SPI interrupt to be executed if SPIF bit in the SPSR Register is ...
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Bits 1, 0 – SPR1, SPR0: SPI Clock Rate Select 1 and 0 These two bits control the SCK rate of the device configured as a Master. SPR1 and SPR0 have no effect on the Slave. The relationship between ...
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SPDR – SPI Data Register Bit 0x2E (0x4E) Read/Write Initial Value The SPI Data Register is a read/write register used for data transfer between the Register File and the SPI Shift Register. Writing to the register initiates data transmission. ...
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USART0 20.1 Features • Full Duplex Operation (Independent Serial Receive and Transmit Registers) • Asynchronous or Synchronous Operation • Master or Slave Clocked Synchronous Operation • High Resolution Baud Rate Generator • Supports Serial Frames with ...
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Figure 20-1. USART Block Diagram Note: 20.3 Clock Generation The Clock Generation logic generates the base clock for the Transmitter and Receiver. The USART supports four modes of clock operation: Normal asynchronous, Double Speed asyn- chronous, Master synchronous and Slave ...
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Figure 20-2 Figure 20-2. Clock Generation Logic, Block Diagram DDR_XCKn Signal description: txclk rxclk xcki operation. xcko fosc 20.3.1 Internal Clock Generation – The Baud Rate Generator Internal clock generation is used for the asynchronous and the synchronous master modes ...
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Table 20-1 ing the UBRRn value for each mode of operation using an internally generated clock source. Table 20-1. Operating Mode Asynchronous Normal mode (U2Xn = 0) Asynchronous Double Speed mode (U2Xn = 1) Synchronous Master mode Note: BAUD f ...
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External Clock External clocking is used by the synchronous slave modes of operation. The description in this section refers to External clock input from the XCKn pin is sampled by a synchronization register to minimize the chance of meta-stability. ...
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A frame starts with the start bit followed by the least significant data bit. Then the next data bits total of nine, are succeeding, ending with the most significant bit. If enabled, the parity bit is inserted ...
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USART Initialization The USART has to be initialized before any communication can take place. The initialization pro- cess normally consists of setting the baud rate, setting frame format and enabling the Transmitter or the Receiver depending on the usage. ...
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For the assembly code, the baud rate parameter is assumed to be stored in the r17:r16 Registers. Assembly Code Example USART_Init: C Code Example #define FOSC 1843200 // Clock Speed #define BAUD 9600 #define MYUBRR FOSC/16/BAUD-1 void main( void ) ...
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XCKn pin will be overridden and used as transmission clock. 20.6.1 Sending Frames with Data Bit A data transmission is initiated by loading the transmit buffer with the data ...
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For the assembly code, the data to be sent is assumed to be stored in registers R17:R16. Assembly Code Example USART_Transmit: C Code Example void USART_Transmit( unsigned int data ) { } ...
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UDRn in order to clear UDREn or disable the Data Register Empty interrupt, otherwise a new interrupt will occur once the interrupt routine terminates. The Transmit Complete (TXCn) Flag bit is set one when the entire frame in the Transmit ...
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UDRn will be masked to zero. The USART has to be initialized before the function can be used. Assembly Code Example USART_Receive: C Code Example unsigned char USART_Receive( void ) { } Note: ...
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Assembly Code Example USART_Receive: ; Wait for data to be received sbis UCSRnA, RXCn rjmp USART_Receive ; Get status and 9th bit, then data from buffer error, return -1 andi r18,(1<<FEn)|(1<<DORn)|(1<<UPEn) breq USART_ReceiveNoError ldi ldi ...
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Receive Compete Flag and Interrupt The USART Receiver has one flag that indicates the Receiver state. The Receive Complete (RXCn) Flag indicates if there are unread data present in the receive buf- fer. This flag is one when unread ...
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The UPEn bit is set if the next character that can be read from the receive buffer had a Parity Error when received and the Parity Checking was enabled at that point (UPMn1 = 1). This bit is valid until ...
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Figure 20-5. Start Bit Sampling When the clock recovery logic detects a high (idle) to low (start) transition on the RxDn line, the start bit detection sequence is initiated. Let sample 1 denote the first zero-sample as shown in the ...
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Figure 20-7. Stop Bit Sampling and Next Start Bit Sampling Sample (U2X = 0) Sample (U2X = 1) The same majority voting is done to the stop bit as done for the other bits in the frame. If the stop ...
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Table 20-2. # (Data+Parity Bit) Table 20-3. # (Data+Parity Bit) The recommendations of the maximum receiver baud rate error was made under the assump- tion that the Receiver and Transmitter equally divides the maximum total error. There are two possible ...
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When the frame type bit (the first stop or the ninth bit) is one, the frame contains an address. When the frame type bit ...
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Register Description 20.10.1 UDRn – USART I/O Data Register n Bit Read/Write Initial Value The USART Transmit Data Buffer Register and USART Receive Data Buffer Registers share the same I/O address referred to as USART Data Register or UDRn. ...
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Data Register Empty interrupt (see description of the UDRIEn bit). UDREn is set after a reset to indicate that the Transmitter is ready. • Bit 4 – FEn: Frame Error This bit is set if the next character in the ...
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Bit 5 – UDRIEn: USART Data Register Empty Interrupt Enable n Writing this bit to one enables interrupt on the UDREn Flag. A Data Register Empty interrupt will be generated only if the UDRIEn bit is written to one, ...
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Bits 5:4 – UPMn1:0: Parity Mode These bits enable and set type of parity generation and check. If enabled, the Transmitter will automatically generate and send the parity of the transmitted data bits within each frame. The Receiver will ...
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Table 20-8. UCPOLn 0 1 20.10.5 UBRRnL and UBRRnH – USART Baud Rate Registers Bit Read/Write Initial Value • Bit 15:12 – Reserved Bits These bits are reserved for future use. For compatibility with future devices, these bit must be ...
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Table 20-9. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies f = 1.0000 MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRRn Error UBRRn 2400 25 0.2% 51 4800 12 0.2% 25 9600 6 -7.0% 12 ...
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Table 20-10. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued 3.6864 MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRRn Error UBRRn 2400 95 0.0% 191 4800 47 0.0% 95 9600 23 0.0% ...
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Table 20-11. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued 8.0000 MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRRn Error UBRRn 2400 207 0.2% 416 4800 103 0.2% 207 9600 51 0.2% ...