ATmega324PA Atmel Corporation, ATmega324PA Datasheet

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ATmega324PA

Manufacturer Part Number
ATmega324PA
Description
Manufacturer
Atmel Corporation
Datasheets

Specifications of ATmega324PA

Flash (kbytes)
32 Kbytes
Pin Count
44
Max. Operating Frequency
20 MHz
Cpu
8-bit AVR
# Of Touch Channels
16
Hardware Qtouch Acquisition
No
Max I/o Pins
32
Ext Interrupts
32
Usb Speed
No
Usb Interface
No
Spi
3
Twi (i2c)
1
Uart
2
Graphic Lcd
No
Video Decoder
No
Camera Interface
No
Adc Channels
8
Adc Resolution (bits)
10
Adc Speed (ksps)
15
Analog Comparators
1
Resistive Touch Screen
No
Temp. Sensor
No
Crypto Engine
No
Sram (kbytes)
2
Eeprom (bytes)
1024
Self Program Memory
YES
Dram Memory
No
Nand Interface
No
Picopower
Yes
Temp. Range (deg C)
-40 to 85
I/o Supply Class
1.8 to 5.5
Operating Voltage (vcc)
1.8 to 5.5
Fpu
No
Mpu / Mmu
no / no
Timers
3
Output Compare Channels
6
Input Capture Channels
1
Pwm Channels
6
32khz Rtc
Yes
Calibrated Rc Oscillator
Yes

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Features
Note:
High-performance, Low-power Atmel
Advanced RISC Architecture
High Endurance Non-volatile Memory segments
QTouch
JTAG (IEEE std. 1149.1 Compliant) Interface
Peripheral Features
Special Microcontroller Features
I/O and Packages
Operating Voltages
Speed Grades
Power Consumption at 1MHz, 1.8V, 25°C
– 131 Powerful Instructions – Most Single-clock Cycle Execution
– 32 x 8 General Purpose Working Registers
– Fully Static Operation
– Up to 20MIPS Throughput at 20MHz
– On-chip 2-cycle Multiplier
– 16/32/64/128KBytes of In-System Self-programmable Flash program memory
– 512/1K/2K/4KBytes EEPROM
– 1/2/4/16KBytes Internal SRAM
– Write/Erase Cycles: 10,000 Flash/ 100,000 EEPROM
– Data retention: 20 years at 85°C/ 100 years at 25°C
– Optional Boot Code Section with Independent Lock Bits
– Programming Lock for Software Security
– Capacitive touch buttons, sliders and wheels
– QTouch and QMatrix acquisition
– Up to 64 sense channels
– Boundary-scan Capabilities According to the JTAG Standard
– Extensive On-chip Debug Support
– Programming of Flash, EEPROM, Fuses, and Lock Bits through the JTAG Interface
– Two 8-bit Timer/Counters with Separate Prescalers and Compare Modes
– One/two 16-bit Timer/Counter with Separate Prescaler, Compare Mode, and Capture Mode
– Real Time Counter with Separate Oscillator
– Six PWM Channels
– 8-channel, 10-bit ADC
– Byte-oriented Two-wire Serial Interface
– Two Programmable Serial USART
– Master/Slave SPI Serial Interface
– Programmable Watchdog Timer with Separate On-chip Oscillator
– On-chip Analog Comparator
– Interrupt and Wake-up on Pin Change
– Power-on Reset and Programmable Brown-out Detection
– Internal Calibrated RC Oscillator
– External and Internal Interrupt Sources
– Six Sleep Modes: Idle, ADC Noise Reduction, Power-save, Power-down, Standby and
– 32 Programmable I/O Lines
– 40-pin PDIP, 44-lead TQFP, 44-pad VQFN/QFN/MLF
– 44-pad DRQFN
– 49-ball VFBGA
– 1.8 - 5.5V
– 0 - 4MHz @ 1.8 - 5.5V
– 0 - 10MHz @ 2.7 - 5.5V
– 0 - 20MHz @ 4.5 - 5.5V
– Active: 0.4mA
– Power-down Mode: 0.1µA
– Power-save Mode: 0.6µA (Including 32kHz RTC)
Extended Standby
In-System Programming by On-chip Boot Program
True Read-While-Write Operation
Differential mode with selectable gain at 1x, 10x or 200x
1. See
®
library support
”Data Retention” on page 9
®
AVR
for details.
®
8-bit Microcontroller
(1)
8-bit Atmel
Microcontroller
with
16/32/64/128K
Bytes In-System
Programmable
Flash
ATmega164A
ATmega164PA
ATmega324A
ATmega324PA
ATmega644A
ATmega644PA
ATmega1284
ATmega1284P
8272C–AVR–06/11

Related parts for ATmega324PA

ATmega324PA Summary of contents

Page 1

... Power-down Mode: 0.1µA – Power-save Mode: 0.6µA (Including 32kHz RTC) Note: 1. See ”Data Retention” on page 9 ® ® AVR 8-bit Microcontroller (1) for details. 8-bit Atmel Microcontroller with 16/32/64/128K Bytes In-System Programmable Flash ATmega164A ATmega164PA ATmega324A ATmega324PA ATmega644A ATmega644PA ATmega1284 ATmega1284P 8272C–AVR–06/11 ...

Page 2

Pin Configurations 1.1 Pinout - PDIP/TQFP/VQFN/QFN/MLF for Figure 1-1. Note: 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P Pinout (PCINT8/XCK0/T0) PB0 (PCINT9/CLKO/T1) PB1 (PCINT10/INT2/AIN0) PB2 (PCINT11/OC0A/AIN1) PB3 (PCINT12/OC0B/SS) PB4 (PCINT13/ICP3/MOSI) PB5 (PCINT14/OC3A/MISO) PB6 (PCINT15/OC3B/SCK) PB7 RESET VCC GND XTAL2 XTAL1 (PCINT24/RXD0/T3) PD0 (PCINT25/TXD0) PD1 ...

Page 3

Pinout - DRQFN for ATmega164A/164PA/324A/324PA Figure 1- Table 1- 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P DRQFN - Pinout Top view B1 B15 B2 B14 B3 B13 ...

Page 4

Pinout - VFBGA for ATmega164A/164PA/324A/324PA Figure 1- Table 1- 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P VFBGA - Pinout Top view BGA - ...

Page 5

Overview The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P is a low-power CMOS 8-bit microcontroller based on the AVR enhanced RISC architecture. By executing powerful instruc- tions in a single clock cycle, the ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P achieves throughputs approaching 1 MIPS per MHz allowing the system designer ...

Page 6

The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P provide the following features: 16/32/64/128Kbytes of In-System Programmable Flash with Read-While-Write capabilities, 512/1K/2K/4Kbytes EEPROM, 1/2/4/16Kbytes SRAM, 32 general purpose I/O lines, 32 general purpose working registers, Real Time Counter (RTC), three flexible Timer/Counters with com- pare modes and ...

Page 7

... Comparison Between ATmega164A, ATmega164PA, ATmega324A, ATmega324PA, ATmega644A, ATmega644PA, ATmega1284 and ATmega1284P Table 2-1. Differences between ATmega164A, ATmega164PA, ATmega324A, ATmega324PA, ATmega644A, ATmega644PA, ATmega1284 and ATmega1284P Device Flash ATmega164A 16 K ATmega164PA 16 K ATmega324A 32 K ATmega324PA 32 K ATmega644A 64 K ATmega644PA 64 K ATmega1284 128 K ATmega1284P 128 K 2 ...

Page 8

As inputs, Port C pins that are externally pulled low will source current if the pull-up resistors are activated. The Port C pins are tri-stated when a reset condition becomes active, even if the clock is not running. Port ...

Page 9

Resources A comprehensive set of development tools, application notes and datasheetsare available for download on http://www.atmel.com/avr. 4. About Code Examples This documentation contains simple code examples that briefly show how to use various parts of the device. Be aware ...

Page 10

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 ...

Page 11

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 ...

Page 12

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 ...

Page 13

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 ...

Page 14

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 ...

Page 15

... R/W R/W R Initial values respectively for the ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P Stack Pointer size Device ATmega164A/ATmega164PA ATmega324A/ATmega324PA ATmega644A/ATmega644PA ATmega1284/ATmega1284P ( RAMPZ7 RAMPZ6 RAMPZ5 R/W R/W R 15. Note that LPM is not affected by the RAMPZ setting. The Z-pointer used by ELPM and SPM ...

Page 16

Figure 7-5. 1st Instruction Execute 2nd Instruction Execute 3rd Instruction Execute Figure 7-6 operation using two register operands is executed, and the result is stored back to the destina- tion register. Figure 7-6. Register Operands Fetch ALU Operation Execute 7.7 ...

Page 17

The I-bit is automatically set when a Return from Interrupt instruction – RETI – is executed. There are basically two types of interrupts. The first type is triggered by an event that ...

Page 18

Assembly Code Example sei sleep; enter sleep, waiting for interrupt ; note: will enter sleep before any pending ; interrupt(s) C Code Example __enable_interrupt(); /* set Global Interrupt Enable */ __sleep(); /* enter sleep, waiting for interrupt */ /* note: ...

Page 19

AVR Memories 8.1 Overview ...

Page 20

Figure 8-1. 8.3 SRAM Data Memory Figure 8-2 Memory is organized. The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P is a complex microcontroller with more peripheral units than can be supported within the 64 location reserved in the Opcode for the IN and OUT instructions. For ...

Page 21

The 32 general purpose working registers, 64 I/O registers, 160 Extended I/O Registers and ...

Page 22

EEPROM Data Memory The ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P contains 512/1K/2K/4Kbytes of data EEPROM memory organized as a separate data space, in which single bytes can be read and written. The EEPROM has an endurance of at least 100,000 write/erase cycles. ...

Page 23

I/O Memory The I/O space definition of the ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P is shown in All ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P I/Os and peripherals are placed in the I/O space. All I/O locations may be accessed by the LD/LDS/LDD and ST/STS/STD instructions, transferring data between the ...

Page 24

Register Description 8.6.1 EEARH and EEARL – The EEPROM Address Register Bit 0x22 (0x42) 0x21 (0x41) Read/Write Initial Value • Bits 15:12 – Reserved These bits are reserved bits in the ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P and will always read as zero. • ...

Page 25

The Programming times for the different modes are shown in While EEPE is set, any write to EEPMn will be ignored. During reset, the EEPMn bits will be reset to 0b00 unless the EEPROM is busy programming. Table 8-1. ...

Page 26

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 ...

Page 27

The following code examples show one assembly and one C function for writing to the EEPROM. The examples assume that interrupts are controlled (e.g. by disabling interrupts glob- ally) so that no interrupts will occur during execution of these functions. ...

Page 28

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: C Code Example unsigned ...

Page 29

GPIOR2 – General Purpose I/O Register 2 Bit 0x2B (0x4B) Read/Write Initial Value 8.6.5 GPIOR1 – General Purpose I/O Register 1 Bit 0x2A (0x4A) Read/Write Initial Value 8.6.6 GPIOR0 – General Purpose I/O Register 0 Bit 0x1E (0x3E) Read/Write ...

Page 30

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 ...

Page 31

Flash Clock – clk FLASH The Flash clock controls operation of the Flash interface. The Flash clock is usually active simul- taneously with the CPU clock. 9.1.4 Asynchronous Timer Clock – clk The Asynchronous Timer clock allows the Asynchronous ...

Page 32

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 Vcc. The delay will not monitor the actual ...

Page 33

Low Power Crystal Oscillator This Crystal Oscillator is a low power oscillator, with reduced voltage swing on the XTAL2 out- put. It gives the lowest power consumption, but is not capable of driving other clock inputs, and may be ...

Page 34

Notes: 9.4 Full Swing Crystal Oscillator This Crystal Oscillator is a full swing oscillator, with rail-to-rail swing on the XTAL2 output. This is useful for driving other clock inputs and in noisy environments. The current consumption is higher than the ...

Page 35

Low Frequency Crystal Oscillator The Low-frequency Crystal Oscillator is optimized for use with a 32.768kHz watch crystal. When selecting crystals, load capasitance and crystal’s Equivalent Series Resistance, ESR must ...

Page 36

To find suitable load capacitance for a 32.768kHz crysal, please consult the crystal datasheet. When this oscillator is selected, start-up times are determined by the SUT Fuses and CKSEL0 as shown in Table 9-9. Power Conditions BOD enabled Fast rising ...

Page 37

When this Oscillator is selected, start-up times are determined by the SUT Fuses as shown in Table 9-11 on page Table 9-11. Power Conditions BOD enabled Fast rising power Slowly rising power Note: 9.7 128kHz Internal Oscillator The 128kHz internal ...

Page 38

External Clock To drive the device from an external clock source, XTAL1 should be driven as shown in 9-4. To run the device on an external clock, the CKSEL Fuses must be programmed to “0000”. Figure 9-4. When this ...

Page 39

Timer/Counter Oscillator ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P uses the same type of crystal oscillator for Low-frequency Crystal Oscillator and Timer/Counter Oscillator. See quency Crystal Oscillator” on page 35 The device can operate its Timer/Counter2 from an external 32.768kHz watch crystal or a exter- ...

Page 40

Register Description 9.12.1 OSCCAL – Oscillator Calibration Register Bit (0x66) Read/Write Initial Value • Bits 7:0 – CAL7:0: Oscillator Calibration Value The Oscillator Calibration Register is used to trim the Calibrated Internal RC Oscillator to remove process variations from ...

Page 41

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 ...

Page 42

Power Management and Sleep Modes 10.1 Overview 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 consumption to the ...

Page 43

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 ...

Page 44

Power-down Mode When the SM2..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, and the ...

Page 45

Power Reduction Register The Power Reduction Register(PRR), see provides 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 or ...

Page 46

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 ...

Page 47

Register Description 10.12.1 SMCR – Sleep Mode Control Register The Sleep Mode Control Register contains control bits for power management. Bit 0x33 (0x53) Read/Write Initial Value • Bits – SM2:0: Sleep Mode Select Bits 2, 1, ...

Page 48

MCUCR – MCU Control Register Bit 0x35 (0x55) Read/Write Initial Value Note: • Bit 6 – BODS: BOD Sleep The BODS bit must be written to logic one in order to turn off BOD during sleep, see on page ...

Page 49

Bit 3 – PRTIM1: Power Reduction Timer/Counter1 Writing a logic one to this bit shuts down the Timer/Counter1 module. When the Timer/Counter1 is enabled, operation will continue like before the shutdown. • Bit 2 – PRSPI: Power Reduction Serial ...

Page 50

System Control and Reset 11.1 Resetting the AVR During reset, all I/O Registers are set to their initial values, and the program starts execution from the Reset Vector. The instruction placed at the Reset Vector must be a JMP ...

Page 51

Figure 11-1. Reset Logic BODLEVEL [2..0] 11.1.2 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 to ...

Page 52

Figure 11-2. MCU Start-up, RESET Tied to V TIME-OUT INTERNAL Figure 11-3. MCU Start-up, RESET Extended Externally TIME-OUT INTERNAL 11.1.3 External Reset An External Reset is generated by a low level on the RESET pin. Reset pulses longer than the ...

Page 53

Brown-out Detection ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P has an On-chip Brown-out Detec- tion (BOD) circuit for monitoring the V level. The trigger level for the BOD can be selected by the BODLEVEL Fuses. The trigger level has a hysteresis to ensure spike free ...

Page 54

Internal Voltage Reference ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P features an internal bandgap ref- erence. This reference is used for Brown-out Detection, and it can be used as an input to the Analog Comparator or the ADC. 11.2.1 Voltage Reference Enable Signals and Start-up ...

Page 55

Watchdog Timer 11.3.1 Features • Clocked from separate On-chip Oscillator • 3 Operating modes – Interrupt – System Reset – Interrupt and System Reset • Selectable Time-out period from 16ms to 8s • Possible Hardware fuse Watchdog always on ...

Page 56

In the same operation, write a logic one to the Watchdog change enable bit (WDCE) and WDE. A logic one must be written to WDE regardless of the previous value of the WDE bit. 2. Within the next four ...

Page 57

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. If the code is not set up to handle the Watchdog, this ...

Page 58

Register Description 11.4.1 MCUSR – MCU Status Register The MCU Status Register provides information on which reset source caused an MCU reset. Bit 0x34 (0x54) Read/Write Initial Value • Bit 4 – JTRF: JTAG Reset Flag This bit is ...

Page 59

WDTCSR – Watchdog Timer Control Register Bit (0x60) Read/Write Initial Value • Bit 7 - WDIF: Watchdog Interrupt Flag This bit is set when a time-out occurs in the Watchdog Timer and the Watchdog Timer is config- ured for ...

Page 60

Bit 5, 2:0 - WDP3:0: Watchdog Timer Prescaler and 0 The WDP3:0 bits determine the Watchdog Timer prescaling when the Watchdog Timer is run- ning. The different prescaling values and their corresponding time-out periods are shown ...

Page 61

Interrupts 12.1 Overview ...

Page 62

Table 12-1. Vector No Notes: Table 12-2 BOOTRST and IVSEL settings. If the program never enables an interrupt source, the Interrupt Vectors are not used, and regular program code can be placed ...

Page 63

The most typical and general program setup for the Reset and Interrupt Vector Addresses in ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P is: Address 0x0000 0x0002 0x0004 0x0006 0x0008 0x000A 0x000C 0x000E 0x0010 0x0012 0x0014 0x0016 0x0018 0x001A 0x001C 0x001E 0x0020 0x0022 0x0024 0x0026 0x0028 0x002A ...

Page 64

Notes: When the BOOTRST Fuse is unprogrammed, the Boot section size set to 8K 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 ...

Page 65

RESET: ldi 0x1F03F 0x1F040 0x1F041 0x1F042 0x1FO43 12.2.1 Moving Interrupts Between Application and Boot Space The General Interrupt Control Register controls the placement of the Interrupt Vector table. 12.3 Register Description 12.3.1 MCUCR – MCU Control ...

Page 66

Assembly Code Example Move_interrupts: C Code Example void Move_interrupts(void) { uchar temp; } 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P ; Get MCUCR in r16, MCUCR mov r17, r16 ; Enable change of Interrupt Vectors ori r16, (1<<IVCE) out MCUCR, r16 ; Move interrupts to ...

Page 67

External Interrupts 13.1 Overview The External Interrupts are triggered by the INT2:0 pin or any of the PCINT31:0 pins. Observe that, if enabled, the interrupts will trigger even if the INT2:0 or PCINT31:0 pins are configured as outputs. This ...

Page 68

If low level interrupt is selected, the low level must be held until the com- pletion of the currently executing instruction to generate an interrupt. If enabled, a level triggered interrupt will generate an interrupt request as ...

Page 69

PCICR – Pin Change Interrupt Control Register Bit (0x68) Read/Write Initial Value • Bit 3 – PCIE3: Pin Change Interrupt Enable 3 When the PCIE3 bit is set (one) and the I-bit in the Status Register (SREG) is set ...

Page 70

Bit 1 – PCIF1: Pin Change Interrupt Flag 1 When a logic change on any PCINT15:8 pin triggers an interrupt request, PCIF1 becomes set (one). If the I-bit in SREG and the PCIE1 bit in PCICR are set (one), ...

Page 71

PCMSK0 – Pin Change Mask Register 0 Bit (0x6B) Read/Write Initial Value • Bit 7:0 – PCINT7:0: Pin Change Enable Mask 7..0 Each PCINT7:0 bit selects whether pin change interrupt is enabled on the corresponding I/O pin. If PCINT7:0 ...

Page 72

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 ...

Page 73

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 ...

Page 74

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 ...

Page 75

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 ...

Page 76

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 mode, ...

Page 77

Unconnected Pins If some pins are unused recommended to ensure that these pins have a defined level. Even though most of the digital inputs are disabled in the deep sleep modes as described above, float- ing inputs ...

Page 78

Alternate Port Functions Most port pins have alternate functions in addition to being general digital I/Os. shows how the port pin control signals from the simplified ridden by alternate functions. The overriding signals may not be present in all ...

Page 79

Table 14-2 ure 14-5 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 each port, and relate the ...

Page 80

Alternate Functions of Port A The Port A pins with alternate functions are shown in Table 14-3. Port Pin PA7 PA6 PA5 PA4 PA3 PA2 PA1 PA0 • ADC7:0/PCINT7:0 – Port A, Bit 7:0 ADC7:0, Analog to Digital Converter, ...

Page 81

Table 14-4 on page 81 overriding signals shown in Table 14-4. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO Table 14-5. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P and ...

Page 82

Alternate Functions of Port B The Port B pins with alternate functions are shown in Table 14-6. Port Pin PB7 PB6 PB5 PB4 PB3 PB2 PB1 PB0 The alternate pin configuration is as follows: • SCK/OC3B/PCINT15 – Port B, ...

Page 83

OC3A, Output Compare Match A output: The PB6 pin can serve as an external output for the Timer/Counter0 Output Compare. The pin has to be configured as an output (DDB6 set “one”) to serve this function. The OC3A pin is ...

Page 84

CLKO, Divided System Clock: The divided system clock can be output on the PB1 pin. The divided system clock will be output if the CKOUT Fuse is programmed, regardless of the PORTB1 and DDB1 settings. It will also be output ...

Page 85

Table 14-8. Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO 14.3.3 Alternate Functions of Port C The Port C pins with alternate functions are shown in Table 14-9. Port Pin PC7 PC6 PC5 PC4 PC3 PC2 ...

Page 86

TOSC1/PCINT22 – Port C, Bit 6 TOSC1, Timer Oscillator pin 1. The PC6 pin can serve as an external interrupt source to the MCU. PCINT22, Pin Change Interrupt source 22: The PC6 pin can serve as an external interrupt ...

Page 87

Table 14-10. Overriding Signals for Alternate Functions in PC7:PC4 Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV DI AIO Table 14-11. Overriding Signals for Alternate Functions in PC3:PC0 Signal Name PUOE PUOV DDOE DDOV PVOE PVOV DIEOE DIEOV ...

Page 88

Alternate Functions of Port D The Port D pins with alternate functions are shown in Table 14-12. Port D Pins Alternate Functions Port Pin PD7 PD6 PD5 PD4 PD3 PD2 PD1 PD0 The alternate pin configuration is as follows: ...

Page 89

OC1A/PCINT29 – Port D, Bit 5 OC1A, Output Compare Match A output: The PD5 pin can serve as an external output for the Timer/Counter1 Output Compare A. The pin has to be configured as an output (DDD5 set (one)) ...

Page 90

PCINT24, Pin Change Interrupt Source 24: The PD0 pin can serve as an external interrupt source. Table 14-13 on page 90 the overriding signals shown in Table 14-13. Overriding Signals for Alternate Functions PD7:PD4 Signal Name PUOE PUOV DDOE DDOV ...

Page 91

Register Description 14.3.5 MCUCR – MCU Control Register Bit 0x35 (0x55) Read/Write Initial Value Note: • 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 ...

Page 92

PORTC – Port C Data Register Bit 0x08 (0x28) Read/Write Initial Value 14.3.13 DDRC – Port C Data Direction Register Bit 0x07 (0x27) Read/Write Initial Value 14.3.14 PINC – Port C Input Pins Address Bit 0x06 (0x26) Read/Write Initial ...

Page 93

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 ...

Page 94

The Timer/Counter is inactive when no clock source is selected. The output from the Clock Select logic is referred to as the timer clock (clk The double buffered Output Compare Registers (OCR0A and ...

Page 95

Depending of the mode of operation used, the counter is cleared, incremented, or decremented at each timer clock (clk selected by the Clock Select bits (CS02:0). When no clock source is selected (CS02:0 = ...

Page 96

Figure 15-3. Output Compare Unit, Block Diagram The OCR0x Registers are 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 dou- ble buffering is ...

Page 97

Similarly, do not write the TCNT0 value equal to BOTTOM when the counter is down-counting. The setup of the OC0x should be performed before setting the Data Direction Register for the port pin to output. The easiest way of ...

Page 98

Compare Output Mode and Waveform Generation The Waveform Generator uses the COM0x1:0 bits differently in Normal, CTC, and PWM modes. For all modes, setting the COM0x1 tells the Waveform Generator that no action on the OC0x Register ...

Page 99

Figure 15-5. CTC Mode, Timing Diagram TCNTn OCn (Toggle) Period An interrupt can be generated each time the counter value reaches the TOP value by using the OCF0A Flag. If the interrupt is enabled, the interrupt handler routine can be ...

Page 100

PWM mode is shown in togram for illustrating the single-slope operation. The diagram includes non-inverted and inverted PWM outputs. The small horizontal line marks on the TCNT0 slopes represent Com- pare Matches between OCR0x and TCNT0. Figure 15-6. Fast PWM ...

Page 101

OC0A toggle in CTC mode, except the double buffer feature of the Out- put Compare unit is enabled in the fast PWM mode. 15.7.4 Phase Correct PWM Mode The phase correct PWM mode (WGM02:0 = ...

Page 102

OC0A pin to toggle on Compare Matches if the WGM02 bit is set. This option is not available for the OC0B pin (See be visible on the port pin if the data direction for the port pin ...

Page 103

Figure 15-9. Timer/Counter Timing Diagram, with Prescaler (f clk clk (clk TCNTn TOVn Figure 15-10 mode and PWM mode, where OCR0A is TOP. Figure 15-10. Timer/Counter Timing Diagram, Setting of OCF0x, with Prescaler (f clk clk (clk TCNTn OCRnx OCFnx ...

Page 104

Register Description 15.9.1 TCCR0A – Timer/Counter Control Register A Bit 0x24 (0x44) Read/Write Initial Value • Bits 7:6 – COM0A1:0: Compare Match Output A Mode These bits control the Output Compare pin (OC0A) behavior. If one or both of ...

Page 105

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 are set, the OC0B output ...

Page 106

Table 15-7 on page 106 to phase correct PWM mode. Table 15-7. COM0B1 Note: • Bits 3:2 – Reserved These bits are reserved bits in the ATmega164A/164PA/324A/324PA/644A/644PA/1284/1284P and will always read as zero. • Bits 1:0 ...

Page 107

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 ...

Page 108

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 ...

Page 109

TIMSK0 – Timer/Counter Interrupt Mask Register Bit (0x6E) Read/Write Initial Value • Bits 7:3 – Reserved These bits are reserved and will always read as zero. • Bit 2 – OCIE0B: Timer/Counter Output Compare Match B Interrupt Enable When ...

Page 110

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 ...

Page 111

Timer/Counter1 and Timer/Counter3 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 • ...

Page 112

Figure 16-1. 16-bit Timer/Counter Block Diagram Note: 16.2.1 Registers The Timer/Counter (TCNTn), Output Compare Registers (OCRnA/B/C), and Input Capture Reg- ister (ICRn) are all 16-bit registers. Special procedures must be followed when accessing the 16- bit registers. These procedures are ...

Page 113

See Section “16.7” on page Flag (OCFnA/B/C) 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 ...

Page 114

Assembly Code Examples C Code Examples Note: The assembly code example returns the TCNTn value in the r17:r16 register pair important to notice that accessing 16-bit registers are atomic operations interrupt occurs between the two instructions ...

Page 115

The following code examples show how atomic read of the TCNTn Register contents. Reading any of the OCRnA/B/C or ICRn Registers can be done by using the same principle. Assembly Code Example TIM16_ReadTCNTn: C Code Example unsigned ...

Page 116

The following code examples show how atomic write of the TCNTn Register contents. Writing any of the OCRnA/B/C or ICRn Registers can be done by using the same principle. Assembly Code Example TIM16_WriteTCNTn: C Code Example void ...

Page 117

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 ...

Page 118

The Timer/Counter Overflow Flag (TOVn) is set according to the mode of operation selected by the WGMn3:0 bits. TOVn can be used for generating a CPU interrupt. 16.6 Input Capture Unit The Timer/Counter incorporates an Input Capture unit that can ...

Page 119

TOP value can be written to the ICRn Register. When writing the ICRn Register the high byte must be written to the ICRnH I/O location before the low byte is written ...

Page 120

I/O bit location). For measuring frequency only, the clearing of the ICFn Flag is not required (if an interrupt handler is used). 16.7 Output Compare Units The 16-bit comparator continuously compares ...

Page 121

PWM pulses, thereby making the out- put glitch-free. The OCRnx Register access may seem complex, but this is not case. When the double buffering is enabled, the CPU has access to the OCRnx Buffer ...

Page 122

Compare Match Output Unit The Compare Output mode (COMnx1:0) bits have two functions. The Waveform Generator uses the COMnx1:0 bits for defining the Output Compare (OCnx) state at the next compare match. Secondly the COMnx1:0 bits control the OCnx ...

Page 123

Compare Output Mode and Waveform Generation The Waveform Generator uses the COMnx1:0 bits differently in normal, CTC, and PWM modes. For all modes, setting the COMnx1 tells the Waveform Generator that no action on the OCnx Register ...

Page 124

The timing diagram for the CTC mode is shown in increases until a compare match occurs with either OCRnA or ICRn, and then counter (TCNTn) is cleared. Figure 16-6. CTC Mode, Timing Diagram TCNTn OCnA (Toggle) Period An interrupt can ...

Page 125

PWM modes that use dual-slope operation. This high frequency makes the fast PWM mode well suited for power regulation, rectification, and DAC applications. High frequency allows physically small sized external components (coils, capaci- tors), ...

Page 126

ICRn value written is lower than the current value of TCNTn. The result will then be that the counter will ...

Page 127

However, due to the symmetric feature of the dual-slope PWM modes, these modes are preferred for motor control applications. The PWM resolution for the phase correct PWM mode can be fixed to 8-, 9-, or 10-bit, or defined by ...

Page 128

OCRnx Registers are written. As the third period shown in TOP actively while the Timer/Counter is running in the phase correct mode can result in an unsymmetrical output. The reason for this can be found in the time of update ...

Page 129

OCRnA 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 ...

Page 130

Using the ICRn Register for defining TOP works well when using fixed TOP values. By using ICRn, the OCRnA Register is free to be used for generating a PWM output on OCnA. However, if the base PWM frequency is actively ...

Page 131

Figure 16-11. Timer/Counter Timing Diagram, Setting of OCFnx, with Prescaler (f Figure 16-12 frequency correct PWM mode the OCRnx Register is updated at BOTTOM. The timing diagrams will be the same, but TOP should be replaced by BOTTOM, TOP-1 by ...

Page 132

Figure 16-13. Timer/Counter Timing Diagram, with Prescaler (f and ICF n 16.11 Register Description 16.11.1 TCCRnA – Timer/Counter n Control Register A Bit (0x80) Read/Write Initial Value • Bit 7:6 – COMnA1:0: Compare Output Mode for Channel A • Bit ...

Page 133

Table 16-3 on page 133 the fast PWM mode. Table 16-3. COMnA1/COMnB1 Note: Table 16-4 on page 133 the phase correct or the phase and frequency correct, PWM mode. Table 16-4. COMnA1/COMnB1 Note: • Bit 1:0 – WGMn1:0: Waveform Generation ...

Page 134

Table 16-5. Waveform Generation Mode Bit Description WGMn2 WGMn1 Mode WGMn3 (CTCn) (PWMn1 ...

Page 135

When the ICRn is used as TOP value (see description of the WGMn3:0 bits located in the TCCRnA and the TCCRnB Register), the ICPn is disconnected and consequently the Input Cap- ture function is disabled. • Bit 5 – Reserved ...

Page 136

A FOCnA/FOCnB strobe will not generate any interrupt nor will it clear the timer in Clear Timer on Compare match (CTC) mode using OCRnA as TOP. The FOCnA/FOCnB bits are always read as zero. 16.11.4 TCNT1H and TCNT1L –Timer/Counter1 Bit ...

Page 137

OCR1BH and OCR1BL – Output Compare Register1 B Bit (0x8B) (0x8A) Read/Write Initial Value The Output Compare Registers contain a 16-bit value that is continuously compared with the counter value (TCNT1). A match can be used to generate an ...

Page 138

High Byte Register (TEMP). This temporary register is shared by all the other 16-bit registers. See “Accessing 16-bit Registers” on page 113. 16.11.11 ICR3H and ICR3L – Input Capture Register 3 Bit (0x97) (0x96) Read/Write Initial Value The Input ...

Page 139

Bit 0 – TOIE1: Timer/Counter1, Overflow Interrupt Enable When this bit is written to one, and the I-flag in the Status Register is set (interrupts globally enabled), the Timer/Counter1 Overflow interrupt is enabled. The corresponding Interrupt Vector (See Section ...

Page 140

Bit 5 – ICF1: Timer/Counter1, Input Capture Flag This flag is set when a capture event occurs on the ICP1 pin. When the Input Capture Register (ICR1) is set by the WGMn3 used as the TOP value, ...

Page 141

Bit 4:3 – Reserved These bits are unused and will always read as zero. • Bit 2 – OCF3B: Timer/Counter3, Output Compare B Match Flag This flag is set in the timer clock cycle after the counter (TCNT3) value ...

Page 142

Timer/Counter2 with PWM and Asynchronous Operation 17.1 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 ...

Page 143

Registers The Timer/Counter (TCNT2) and Output Compare Register (OCR2A and OCR2B) are 8-bit reg- isters. Interrupt request (abbreviated to Int.Req.) signals are all visible in the Timer Interrupt Flag Register (TIFR2). All interrupts are individually masked with the Timer ...

Page 144

Counter Unit The main part of the 8-bit Timer/Counter is the programmable bi-directional counter unit. 17-2 shows a block diagram of the counter and its surrounding environment. Figure 17-2. Counter Unit Block Diagram Signal description (internal signals): count direction ...

Page 145

WGM22:0 bits and Compare Output mode (COM2x1:0) bits. The max and bottom signals are used by the Waveform Generator for handling the special cases of the extreme values in some modes of operation ...

Page 146

Using the Output Compare Unit Since writing TCNT2 in any mode of operation will block all compare matches for one timer clock cycle, there are risks involved when changing TCNT2 when using the Output Compare channel, independently of whether ...

Page 147

Register bit for the OC2x pin (DDR_OC2x) must be set as output before the OC2x value is visi- ble on the pin. The port override function is independent of the Waveform Generation mode. The design of the Output Compare pin ...

Page 148

The timing diagram for the CTC mode is shown in (TCNT2) increases until a compare match occurs between TCNT2 and OCR2A, and then coun- ter (TCNT2) is cleared. Figure 17-5. CTC Mode, Timing Diagram TCNTn OCnx (Toggle) Period An interrupt ...

Page 149

DAC applications. High frequency allows physically small sized external components (coils, capacitors), and therefore reduces total system cost. In fast PWM mode, the counter is incremented until the counter value matches the TOP value. The ...

Page 150

A frequency (with 50% duty cycle) waveform output in fast PWM mode can be achieved by set- ting OC2x to toggle its logical level on each compare match (COM2x1:0 = 1). The waveform generated will have a maximum frequency of ...

Page 151

In phase correct PWM mode, the compare unit allows generation of PWM waveforms on the OC2x pin. Setting the COM2x1:0 bits to two will produce a non-inverted PWM. An inverted PWM output can be generated by setting the COM2x1:0 to ...

Page 152

Figure 17-8. Timer/Counter Timing Diagram, no Prescaling clk clk (clk TCNTn TOVn Figure 17-9 on page 152 Figure 17-9. Timer/Counter Timing Diagram, with Prescaler (f clk clk (clk TCNTn TOVn Figure 17-10 on page 152 Figure 17-10. Timer/Counter Timing Diagram, ...

Page 153

Figure 17-11 on page 153 Figure 17-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres- (clk TCNTn (CTC) OCRnx OCFnx 17.9 Asynchronous Operation of Timer/Counter2 When Timer/Counter2 operates asynchronously, some considerations must be taken. • Warning: When ...

Page 154

OCR2xUB bit returns to zero, the device will never receive a compare match interrupt, and the MCU will not wake up. • If Timer/Counter2 is used to wake the device up from Power-save or ADC Noise Reduction ...

Page 155

Timer/Counter Prescaler Figure 17-12. Prescaler for Timer/Counter2 The clock source for Timer/Counter2 is named clk system I/O clock clk clocked from the TOSC1 pin. This enables use of Timer/Counter2 as a Real Time Counter (RTC). When AS2 is set, ...

Page 156

Register Description 17.11.1 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 ...

Page 157

Table 17-4 rect PWM mode. Table 17-4. 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 ...

Page 158

Note: Table 17-7 rect PWM mode. Table 17-7. COM2B1 Note: • Bits 3:2 – Reserved These bits are reserved and will always read as zero. • Bits 1:0 – WGM21:0: Waveform Generation Mode Combined with the ...

Page 159

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 ...

Page 160

Table 17-9. CS22 17.11.3 TCNT2 – Timer/Counter Register Bit (0xB2) Read/Write Initial Value The Timer/Counter Register gives direct access, both for read and write operations, to the Timer/Counter unit 8-bit counter. Writing ...

Page 161

ASSR – Asynchronous Status Register Bit (0xB6) Read/Write Initial Value • Bit 6 – EXCLK: Enable External Clock Input When EXCLK is written to one, and asynchronous clock is selected, the external clock input buf- fer is enabled and ...

Page 162

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. 17.11.7 TIMSK2 – ...

Page 163

Bit 0 – TOV2: Timer/Counter2 Overflow Flag The TOV2 bit is set (one) when an overflow occurs in Timer/Counter2. TOV2 is cleared by hard- ware when executing the corresponding interrupt handling vector. Alternatively, TOV2 is cleared by writing a ...

Page 164

SPI – Serial Peripheral Interface 18.1 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 ...

Page 165

The interconnection between Master and Slave CPUs with SPI is shown in tem 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 of the ...

Page 166

When the SPI is enabled, the data direction of the MOSI, MISO, SCK, and SS pins is overridden according to Functions” on page Table 18-1. Pin MOSI MISO SCK SS Note: The following code examples show how to initialize the ...

Page 167

Assembly Code Example SPI_MasterInit: SPI_MasterTransmit: Wait_Transmit: C Code Example void SPI_MasterInit(void void SPI_MasterTransmit(char cData Note: 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P (1) ; Set MOSI and SCK output, all others input r17,(1<<DD_MOSI)|(1<<DD_SCK) ldi out DDR_SPI,r17 ; Enable SPI, Master, set ...

Page 168

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: SPI_SlaveReceive: C Code Example void SPI_SlaveInit(void char SPI_SlaveReceive(void Note: 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P (1) ...

Page 169

SS Pin Functionality 18.3.1 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 ...

Page 170

Table 18-2. SPI Mode Figure 18-3. SPI Transfer Format with CPHA = 0 Figure 18-4. SPI Transfer Format with CPHA = 1 8272C–AVR–06/11 ATmega164A/PA/324A/PA/644A/PA/1284/P SPI Modes Conditions 0 CPOL=0, CPHA=0 1 CPOL=0, CPHA=1 2 CPOL=1, CPHA=0 3 CPOL=1, CPHA=1 SCK ...

Page 171

Register Description 18.5.1 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 ...

Page 172

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 SCK ...

Page 173

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. ...

Page 174

USART 19.1 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 ...

Page 175

Figure 19-1. USART Block Diagram Note: The dashed boxes in the block diagram separate the three main parts of the USART (listed from the top): Clock Generator, Transmitter and Receiver. Control Registers are shared by all units. The Clock Generation ...

Page 176

UCSRnA Register. When using synchronous mode (UMSELn = 1), the Data Direction Register for the XCKn pin (DDR_XCKn) controls whether the clock source is internal (Master mode) or external (Slave mode). The XCKn pin is only active when using synchronous ...

Page 177

Table 19-1. Operating Mode Asynchronous Normal mode (U2Xn = 0) Asynchronous Double Speed mode (U2Xn = 1) Synchronous Master mode f OSC UBRRn Some examples of UBRRn values for some system clock frequencies are found in page 197. 19.4.2 Double ...

Page 178

CPU clock period delay and therefore the maximum external XCKn clock frequency is limited by the following equation: Note that f add some margin to avoid possible loss of data due to frequency variations. 19.4.4 Synchronous Clock ...

Page 179

Figure 19-4. Frame Formats St ( IDLE The frame format used by the USART is set by the UCSZn2:0, UPMn1:0 and USBSn bits in UCSRnB and UCSRnC. The Receiver and Transmitter use the same setting. Note that changing ...

Page 180

Note that the TXCn Flag must be cleared before each transmission (before UDRn is written used for this purpose. The following simple USART initialization code examples ...

Page 181

Sending Frames with Data Bit A data transmission is initiated by loading the transmit buffer with the data to be transmitted. The CPU can load the transmit buffer by writing to the UDRn I/O location. The ...

Page 182

Assembly Code Example USART_Transmit: C Code Example void USART_Transmit( unsigned int data ) { } Notes: The ninth bit can be used for indicating an address frame when using multi processor communi- cation mode or for other protocol handling as ...

Page 183

Data Register Empty interrupt routine must either write new data to 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 ...

Page 184

Assembly Code Example USART_Receive: C Code Example unsigned char USART_Receive( void ) { } Note: The function simply waits for data to be present in the receive buffer by checking the RXCn Flag, before reading the buffer and returning the ...

Page 185

Assembly Code Example USART_Receive: USART_ReceiveNoError: C Code Example unsigned int USART_Receive( void ) { } Note: The receive function example reads all the I/O Registers into the Register File before any com- putation is done. This gives an optimal receive ...

Page 186

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 ...

Page 187

The Parity Error (UPEn) Flag can then be read by software to check if the frame had a Parity Error. The UPEn bit is set if the next character that can be read ...

Page 188

Double Speed mode (U2Xn = 1) of operation. Samples denoted zero are samples done when the RxDn line is idle (i.e., no communication activity). Figure 19-5. Start Bit Sampling Sample (U2X = 0) Sample ...

Page 189

Figure 19-7. Stop Bit Sampling and Next Start Bit Sampling The same majority voting is done to the stop bit as done for the other bits in the frame. If the stop bit is registered to have a logic 0 ...

Page 190

Table 19-2. # (Data+Parity Bit) Table 19-3. # (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 ...

Page 191

When the frame type bit is zero the frame is a data frame. The Multi-processor Communication mode enables several slave MCUs to ...

Page 192

Register Description 19.11.1 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. ...

Page 193

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 receive ...

Page 194

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, ...

Page 195

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 ...

Page 196

Bit 0 – UCPOLn: Clock Polarity This bit is used for synchronous mode only. Write this bit to zero when asynchronous mode is used. The UCPOLn bit sets the relationship between data output change and data input sample, and ...

Page 197

Examples of Baud Rate Setting For standard crystal and resonator frequencies, the most commonly used baud rates for asyn- chronous operation can be generated by using the UBRR settings in UBRR values which yield an actual baud rate differing ...

Page 198

Table 19-10. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued 3.6864MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRR Error UBRR 2400 95 0.0% 191 4800 47 0.0% 95 9600 23 0.0% 47 ...

Page 199

Table 19-11. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued 8.0000MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRR Error UBRR 2400 207 0.2% 416 4800 103 0.2% 207 9600 51 0.2% 103 ...

Page 200

Table 19-12. Examples of UBRRn Settings for Commonly Used Oscillator Frequencies (Continued 16.0000MHz osc Baud U2Xn = 0 U2Xn = 1 Rate (bps) UBRR Error UBRR 2400 416 -0.1% 832 4800 207 0.2% 416 9600 103 0.2% 207 ...

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