78
4317I–AVR–01/08
AT90PWM2/3/2B/3B
XTAL1: Chip clock Oscillator pin 1. Used for all chip clock sources except internal calibrated RC
Oscillator. When used as a clock pin, the pin can not be used as an I/O pin.
OC0B, Output Compare Match B output: This pin can serve as an external output for the
Timer/Counter0 Output Compare B. The pin has to be configured as an output (DDE1 set “one”)
to serve this function. This pin is also the output pin for the PWM mode timer function.
• RESET/OCD – Bit 0
RESET, Reset pin: When the RSTDISBL Fuse is programmed, this pin functions as a normal I/O
pin, and the part will have to rely on Power-on Reset and Brown-out Reset as its reset sources.
When the RSTDISBL Fuse is unprogrammed, the reset circuitry is connected to the pin, and the
pin can not be used as an I/O pin.
If PE0 is used as a reset pin, DDE0, PORTE0 and PINE0 will all read 0.
relates the alternate functions of Port E to the overriding signals shown in
11.4
Register Description for I/O-Ports
11.4.1
Port B Data Register – PORTB
11.4.2
Port B Data Direction Register – DDRB
Table 11-13. Overriding Signals for Alternate Functions in PE2..PE0
Signal Name
PE2/ADC0/
XTAL2
PE1/OC0B
PE0/RESET/
OCD
PUOE
0
0
0
PUOV
0
0
0
DDOE
0
0
0
DDOV
0
0
0
PVOE
0
OC0Ben
0
PVOV
0
OC0B
0
DIEOE
ADC0D
0
0
DIEOV
0
0
0
DI
AIO
Osc Output
ADC0
Osc / Clock input
Bit
7
6
5
4
3
2
1
0
PORTB7
PORTB6
PORTB5
PORTB4
PORTB3
PORTB2
PORTB1
PORTB0
PORTB
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
Initial Value
0
0
0
0
0
0
0
0
Bit
7
6
5
4
3
2
1
0
DDB7
DDB6
DDB5
DDB4
DDB3
DDB2
DDB1
DDB0
DDRB
Read/Write
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W
