Datasheet
141
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
Figure 15-1. Timer/Counter4 Block Diagram
15.2.1 Speed
The maximum speed of the Timer/Counter4 is 64MHz. However, if a supply voltage below 4V is used, it is
recommended to decrease the input frequency, because the Timer/Counter4 is not running fast enough on low
voltage levels.
15.2.2 Accuracy
The Timer/Counter4 is a 10-bit Timer/Counter module that can alternatively be used as an 8-bit Timer/Counter.
The Timer/Counter4 registers are basically 8-bit registers, but on top of that there is a 2-bit High Byte Register
(TC4H) that can be used as a common temporary buffer to access the two MSBs of the 10-bit Timer/Counter4
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/Counter4 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 TC4H register, and when writing the low byte of
any 8-bit register the two MSBs are written from the TC4H register. Special procedures must be followed when
accessing the 10-bit Timer/Counter4 values via the 8-bit data bus. These procedures are described in the
section “Accessing 10-bit Registers” on page 160.
The Enhanced PWM mode allows to add a resolution bit to each Compare register A/B/D, while the output
frequency remains identical to a Normal PWM mode. That means that the TC4H register contains one more bit
that will be the MSB in a 11-bits enhanced PWM operation. See the section “Enhanced Compare/PWM mode”
on page 150 for details about this feature and how to use it.
15.2.3 Registers
The Timer/Counter (TCNT4) and Output Compare Registers (OCR4A, OCR4B, OCR4C and OCR4D) are 8-bit
registers that are used as a data source to be compared with the TCNT4 contents. The OCR4A, OCR4B and
OCR4D registers determine the action on the OC4A, OC4B and OC4D pins and they can also generate the
8-BIT DATABUS
T/C INT. FLAG
REGISTER (TIFR4)
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER A (OCR4A)
T/C INT. MASK
REGISTER (TIMSK4)
TIMER/COUNTER4
(TCNT4)
DIRECTION
TIMER/COUNTER4 CONTROL LOGIC
OCF4B
TOV4
TOIE4
OCIE4B
OCIE4A
OCF4A
TOV4 OCF4B OC4AOCF4A
T/C CONTROL
REGISTER A (TCCR4A)
COM4B1
PWM4A
PWM4B
COM4B0
FOC4A
FOC4B
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER B (OCR4B)
COM4A1
COM4A0
T/C CONTROL
REGISTER B (TCCR4B)
CS42
PSR4
CS41
CS40
CS43
OC4A
OC4B
OC4B
DEAD TIME GENERATOR
DEAD TIME GENERATOR
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER C (OCR4C)
10-BIT COMPARATOR
8-BIT OUTPUT COMPARE
REGISTER D (OCR4D)
COM4A1
PWM4D
COM4A0
FOC4D
T/C CONTROL
REGISTER C (TCCR4C)
OCF4D
OCF4D
OCIE4D
OC4D
OC4D
DEAD TIME GENERATOR
PSR4
PSR4
OCW4A
OCW4B
OCW4D
2-BIT HIGH BYTE
REGISTER (TC4H)
WGM41
FPEN4
T/C CONTROL
REGISTER D (TCCR4E)
COM4B1
COM4B0
COM4D1
COM4D0
FPNC4
FPES4
FPAC4
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 (TCCR4D)
FAULT_PROTECTION
WGM40
FPIE4
FPF4
OC4OE5
OC4OE4
OC4OE3
OC4OE2
OC4OE1
OC4OE0
FPIE4
FPF4