14.4.8.2 Alternate Functions of Port B

The Port B pins with alternate functions are shown in the table below:

Table 14-8. Port B Pins Alternate Functions
Port PinAlternate Functions
PB[0]

ADC4: ADC Input Channel 4

PCINT8: Pin Change Interrupt source 8

PB[1]

ADC5: ADC Input Channel 5

OC0A: Timer/Counter0 Compare Match A Output (default
    location)

PCINT9: Pin Change Interrupt source 9

INT0: External Interrupt 0 Source

CLKO: System Clock Output

PB[2]

ADC6: ADC Input Channel 6

ICP0: Timer/Counter0 Input Capture Input (default
    location)

TxD0: USART Output

PCINT10: Pin Change Interrupt source 10

PB[3]

ACO: AC Output

ADC7: ADC Input Channel 7

T0: Timer/Counter0 Clock Source (alternative location)

RxD0: USART Input

PCINT11: Pin Change Interrupt source 11

The alternate pin configuration is as follows:
  • PB[0] – ADC4/PCINT8
    • ADC4: Analog to Digital Converter, Channel 4.
    • PCINT8: Pin Change Interrupt source 8. The PB[0] pin can serve as an external interrupt source for pin change interrupt 1.
  • PB[1] – ADC5/OC0A/PCINT9/INT0/CLKO
    • ADC5: Analog to Digital Converter, Channel 5
    • OC0A: Output Compare Match output. The PB[1] pin can serve as an external output for the Timer/Counter0 Compare Match A. The PB[1] pin has to be configured as an output (DDB0 set (one)) to serve this function. The OC0A pin is also the output pin for the PWM mode timer function.
    • PCINT9: Pin Change Interrupt source 9. The PB[1] pin can serve as an external interrupt source for pin change interrupt 1.
    • INT0: External Interrupt Request 0.
    • CLKO: System Clock Output. The system clock can be output on pin PB[1]. The system clock will be output if CKOUT bit is programmed, regardless of the PORTB2 and DDB2 settings.
  • PB[2] – ADC6/ICP0/TxD0/PCINT10
    • ADC6: Analog to Digital Converter, Channel 6.
    • ICP0: Input Capture Pin. The PB[2] pin can act as an Input Capture pin for Timer/Counter0.
    • PCINT10: Pin Change Interrupt source 10. The PB[2] pin can serve as an external interrupt source for pin change interrupt 1.
    • TxD0: USART Output
  • PB[3] – ACO/ADC7/T0/RXD0/PCINT3/RXD0
    • ACO: AC Output
    • ADC7: Analog to Digital Converter, Channel 7.
    • T0: Timer/Counter0 counter source.
    • PCINT11: Pin Change Interrupt source 11. The PB[3] pin can serve as an external interrupt source for pin change interrupt 1.
    • RXD0: USART input

The following tables relate the alternate functions of Port B to the overriding signals shown in the figure of Alternate Port Functions.

Table 14-9. Overriding Signals for Alternate Functions in PB[3:2]
Signal 
NamePB3/ADC7/ACO/RxD0/T0/PCINT11PB2/ADC6/TxD0/ICP0/PCINT10
PUOEACOETxEN0
PUOV00
DDOERxEN0 + (RxEN0 • ACOE)TxEN0
DDOVACOETxEN0
PVOEACOETxEN0
PVOVACO • ACOETxEN0• TXD0_OUT
PTOE00
DIEOE(PCINT11 • PCIE1) + ADC7D(PCINT10 • PCIE1) + ADC6D
DIEOVPCINT11• PCIE1PCINT10 • PCIE1
DIRxD0/T0/PCINT11 InputICP0/PCINT10 input
AIOADC7/ AC OutputADC6
Table 14-10. Overriding Signals for Alternate Functions in PB[1:0]
Signal 
NamePB1/ADC5/INT0/XCK0/CLKO/OC0A/PCINT9PB0/ADC4/PCINT8
PUOECKOUT(1)0
PUOV00
DDOECKOUT(1)+ (OC0A Enable • REMAP) + XCK0_MASTER0
DDOVCLKO + (CKOUT • OC0A Enable • REMAP • OC0A) + (CKOUT • (OC0A Enable + REMAP) • XCK0_MASTER • XCK0_OUT)0
PVOECKOUT(1)0
PVOV(system clock)0
PTOE00
DIEOE(PCINT9 • PCIE1) + ADC5D + INT0(PCINT8 • PCIE1) + ADC4D
DIEOV(PCINT9 • PCIE1) + INT0(PCINT8 • PCIE1)
DIINT0/PCINT1 InputPCINT8 Input
AIOADC5ADC4
Note:
  1. CKOUT is 1 when the configuration bit is “0” (Programmed).