Register Description For I/O-Ports - Atmel AT90PWM2 Manual

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
AT90PWM2/3/2B/3B
78
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.
Table 11-13 relates the alternate functions of Port E to the overriding signals shown in
11-5 on page 67.
Table 11-13. Overriding Signals for Alternate Functions in PE2..PE0
PE2/ADC0/
Signal Name XTAL2
PUOE 0
PUOV 0
DDOE 0
DDOV 0
PVOE 0
PVOV 0
DIEOE ADC0D
DIEOV 0
DI
Osc Output
AIO
ADC0
Bit 7
PORTB7 PORTB6
Read/Write R/W
Initial Value 0
Bit 7
DDB7 DDB6
Read/Write R/W
PE1/OC0B
0
0
0
0
OC0Ben
OC0B
0
0
Osc / Clock input
6 5 4
PORTB5 PORTB4
R/W R/W R/W
0 0 0
6 5 4
DDB5 DDB4
R/W R/W R/W
PE0/RESET/
OCD
0
0
0
0
0
0
0
0
3 2 1
PORTB3 PORTB2 PORTB1
R/W R/W R/W
0 0 0
3 2 1
DDB3 DDB2 DDB1
R/W R/W R/W
Figure
0
PORTB0 PORTB
R/W
0
0
DDB0 DDRB
R/W
4317I–AVR–01/08