Port F - Motorola DragonBall MC68328 User Manual

puts. Note that the actual value on the pin is reported when these bits are read regardless
of whether they are configured as input or output. These bits reset to 0.
PULLUP - PU[7:0]
These bits enable the pullup resistors on the port. While high, the pullup resistors are en-
abled; while low, they are disabled. Port E, bit 7 pullup resistor is enabled after reset.
SELECT- SEL[7:0]
These bits select whether CSA1B-CSB3B or I/O port signals are connected to the pins.
While high, the port I/O functions are connected to the pin; while low, the chip-select func-
tion is connected.

7.1.7 Port F

Port F is multiplexed with address lines A23-A31. Unused address pins can serve as parallel
I/Os on a bit-by-bit basis. The programmer's model for port F is shown below.
15 14 13 12
DIRECTION
DIR7 DIR6 DIR5 DIR4
Address: $FFFFF428
15 14 13 12
PU7 PU6 PU5 PU4
Address: $FFFFF42A
DIRECTION- DIR[7:0]
These bits control the pin directions. While high, the pins are outputs; while low, the pins
are inputs. These bits reset to 0 and have no function while the select bits are low.
DATA- D[7:0]
These bits control or report the data on the pins while the associated SELECT bits are
high. While the DIRECTION bits are high, D[7:0] controls the data to the pins. While the
DIRECTION bits are low, D[7:0] reports the signal driving the pins. These bits reset to 0
while the SELECT bits are low. The data bits may be written at any time. Bits that are con-
figured as inputs will accept the written data but it will not be accessible until the respective
MOTOROLA MC68328 DRAGONBALL PROCESSOR USER'S MANUAL
11 10 9
DIR3 DIR2 DIR1
Figure 7-16. Port F Data/Direction Register
11 10 9
PULLUP
PU3 PU2 PU1
Figure 7-17. Port F Select Register
8 7 6 5
DIR0 D7 D6 D5
8 7 6 5
PU0 SEL7 SEL6 SEL5
Parallel Ports
4 3 2 1
DATA
D4 D3 D2 D1
Reset Value: $0000
4 3 2 1
SELECT
SEL4 SEL3 SEL2 SEL1
Reset Value: $FFFF
0
D0
0
SEL0
7-9