ATTINY861A-SU Atmel, ATTINY861A-SU Datasheet - Page 88

• Manufacturer Part Number: ATTINY861A-SU
• Description: IC, MCU, 8BIT, 8K FLASH, 20SOIC
• Manufacturer: Atmel

Specifications of ATTINY861A-SU

• Controller Family/series: ATtiny
• No. Of I/o's: 16
• Eeprom Memory Size: 512Byte
• Ram Memory Size: 512Byte
• Cpu Speed: 20MHz
• No.: RoHS Compliant
• Core Size: 8bit
• Program Memory Size: 8KB
• Oscillator Type: External, Internal
• Rohs Compliant: Yes

12.2.1
12.2.2
12.2.3
12.2.4
88
ATtiny261A/461A/861A
Speed
Accuracy
Registers
Synchronization
For actual placement of the I/O pins, refer to
device-specific I/O register and bit locations are listed in the
The maximum speed of the Timer/Counter1 is 64 MHz. However, if a supply voltage below 2.7
volts is used, it is recommended to use the Low Speed Mode (LSM), because the
Timer/Counter1 is not running fast enough on low voltage levels. In the Low Speed Mode the
fast peripheral clock is scaled down to 32 MHz. For more details about the Low Speed Mode,
see
The Timer/Counter1 is a 10-bit Timer/Counter module that can alternatively be used as an 8-bit
Timer/Counter. The Timer/Counter1 registers are basically 8-bit registers, but on top of that
there is a 2-bit High Byte Register (TC1H) that can be used as a common temporary buffer to
access the two MSBs of the 10-bit Timer/Counter1 registers by the AVR CPU via the 8-bit data
bus, if the 10-bit accuracy is used. Whereas, if the two MSBs of the 10-bit registers are written to
zero the Timer/Counter1 is working as an 8-bit Timer/Counter. When reading the low byte of any
8-bit register the two MSBs are written to the TC1H register, and when writing the low byte of
any 8-bit register the two MSBs are written from the TC1H register. Special procedures must be
followed when accessing the 10-bit Timer/Counter1 values via the 8-bit data bus. These proce-
dures are described in the section
The Timer/Counter (TCNT1) and Output Compare Registers (OCR1A, OCR1B, OCR1C and
OCR1D) are 8-bit registers that are used as a data source to be compared with the TCNT1 con-
tents. The OCR1A, OCR1B and OCR1D registers determine the action on the OC1A, OC1B and
OC1D pins and they can also generate the compare match interrupts. The OCR1C holds the
Timer/Counter TOP value, i.e. the clear on compare match value. The Timer/Counter1 High
Byte Register (TC1H) is a 2-bit register that is used as a common temporary buffer to access the
MSB bits of the Timer/Counter1 registers, if the 10-bit accuracy is used.
Interrupt request (overflow TOV1, and compare matches OCF1A, OCF1B, OCF1D and fault pro-
tection FPF1) signals are visible in the Timer Interrupt Flag Register (TIFR) and Timer/Counter1
Control Register D (TCCR1D). The interrupts are individually masked with the Timer Interrupt
Mask Register (TIMSK) and the FPIE1 bit in the Timer/Counter1 Control Register D (TCCR1D).
Control signals are found in the Timer/Counter Control Registers TCCR1A, TCCR1B, TCCR1C,
TCCR1D and TCCR1E.
In asynchronous clocking mode the Timer/Counter1 and the prescaler allow running the CPU
from any clock source while the prescaler is operating on the fast peripheral clock (PCK) having
frequency of 64 MHz (or 32 MHz in Low Speed Mode). This is possible because there is a syn-
chronization boundary between the CPU clock domain and the fast peripheral clock domain.
Figure 12-2
chronization delays in between registers. Note that all clock gating details are not shown in the
figure.
The Timer/Counter1 register values go through the internal synchronization registers, which
cause the input synchronization delay, before affecting the counter operation. The registers
TCCR1A, TCCR1B, TCCR1C, TCCR1D, OCR1A, OCR1B, OCR1C and OCR1D can be read
“PLLCSR – PLL Control and Status Register” on page
shows Timer/Counter 1 synchronization register block diagram and describes syn-
“Accessing 10-Bit Registers” on page
“Pinout ATtiny261A/461A/861A” on page
118.
“Register Description” on page
106.
8197B–AVR–01/10
2. The
110.