Rainbow Electronics ATtiny861_V - Manual (Page 92)

92
2588B–AVR–11/06
ATtiny261/461/861
Figure 16-1. Timer/Counter1 Block Diagram
16.2.1 Speed
The maximum speed of the Timer/Counter1 is 64 MHz. However, if a supply voltage below 2.7
volts is used, it is highly 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
”PLLCSR – PLL Control and Status Register” on page 89 .
16.2.2 Accuracy
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
”Accessing 10-Bit Registers” on page 110 .
16.2.3 Registers
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
8-BIT DATABUS
T/C INT. FLAG
REGISTER (TIFR)
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER A (OCR1A)
T/C INT. MASK
REGISTER (TIMSK)
TIMER/COUNTER1
(TCNT1)
DIRECTION
TIMER/COUNTER1 CONTROL LOGIC
OCF1B TOV1 TOIE1 OCIE1B OCIE1A OCF1A
TOV1 OCF1B OC1A OCF1A
T/C CONTROL
REGISTER A (TCCR1A)
COM1B1 PWM1A PWM1B COM1B0 FOC1A FOC1B
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER B (OCR1B)
COM1A1 COM1A0
T/C CONTROL
REGISTER B (TCCR1B)
CS12 PSR1 CS11 CS10 CS13
OC1A OC1B OC1B
DEAD TIME GENERATOR DEAD TIME GENERATOR
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER C (OCR1C)
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER D (OCR1D)
COM1A1 PWM1D COM1A0 FOC1D
T/C CONTROL
REGISTER C (TCCR1C)
OCF1D
OCF1D OCIE1D
OC1D OC1D
DEAD TIME GENERATOR
PSR1 PSR1
OCW1A
OCW1B
OCW1D
2-BIT HIGH BYTE
REGISTER (TC1H)
WGM11 FPEN1
T/C CONTROL
REGISTER D (TCCR1E)
COM1B1 COM1B0 COM1D1 COM1D0 FPNC1 FPES1 FPAC1
10-BIT OUTPUT
COMPARE REGISTER B 10-BIT OUTPUT
COMPARE REGISTER C 10-BIT OUTPUT
COMPARE REGISTER D 10-BIT OUTPUT
COMPARE REGISTER A
CLEAR
COUNT
CLK
T/C CONTROL
REGISTER C (TCCR1D)
FAULT_PROTECTION
WGM10 FPIE1 FPF1
OC1OE5 OC1OE4 OC1OE3 OC1OE2 OC1OE1 OC1OE0
FPIE1 FPF1