Port Pins Register; Port Direction Register - Motorola MC68306 User Manual

Port B pins can be individually programmed as either IRQ, IACK or parallel port signals.
To use any of the port B pins PB7–PB4 as interrupt request signals (IRQ6, IRQ5, IRQ3,
IRQ2) be sure the bit is programmed as an input. Interrupt enables are provided for each
interrupt level.
To use any of the port B pins PB3–PB0 as IACK6 , IACK5, IACK3, or IACK2, program the
port data bit and the autovector bit to zero.
To use any of the port B pins PB3–PB0 as port inputs, ensure that the autovector bit is
one.
Open-drain or open-source operation can be emulated by programming the appropriate
fixed data (e.g. 0 = open-drain) and toggling the direction control. PB7–PB4 pins can be
programmed as outputs even when enabled as interrupt inputs, allowing inputs to be
tested or emulated if the interrupt is open-drain or open-source. The active interrupt level
is the inverse of the IX register bit.

5.2.5.1 PORT PINS REGISTER

FFFFFFF4/5
15 14 13 12
PA7 PA6 PA5 PA4
RESE
T:
PA6 PA5 PA4
PA7
The port pin register bits are the data at the port pins, regardless of pin direction. The
port pins register is read-only, writes are ignored.

5.2.5.2 PORT DIRECTION REGISTER

FFFFFFF2/3
15 14 13 12
PADIR PADIR PADIR PADIR
7 6 5 4
RESE
T:
0 0 0
0
The port direction register bits determine the direction of data flow at the port pins.
PADIR7–0—Port A Direction Register Bit 7–0
This bit determines the direction of data flow at port A pins 7 through 0.
0 = Input.
1 = Output.
PBDIR7–0—Port B Direction Register Bit 7–0
MOTOROLA
11 10 9 8
PA3 PA2 PA1 PA0
PA3 PA2 PA1 PA0
11 10 9 8
PADIR PADIR PADIR PADIR
3 2 1 0
0 0 0 0
MC68306 USER'S MANUAL
7 6 5
PB7 PB6 PB5 PB4
PB7 PB6 PB5 PB4
7 6 5
PBDIR PBDIR PBDIR5 PBDIR4
7 6
0 0 0
4 3 2 1
PB3 PB2 PB1
PB3 PB2 PB1
SUPERVISOR ONLY
4 3 2 1
PBDIR3 PBDIR2 PBDIR
1
0 0 0 0
SUPERVISOR ONLY
0
PB0
PB0
0
PBDIR
0
0
5- 7