Port E - Motorola DragonBall MC68328 User Manual

Parallel Ports

7.1.6 Port E

Port E is multiplexed with 7 chip-select signals that are identified below.
All 8 bits are implemented in the registers, but only bits 7-1 connect to the outside. As with
other ports, each bit can be individually configured, as needed. The programmer's model for
port E is shown below.
15 14 13 12
DIRECTION
DIR7 DIR6 DIR5 DIR4
Address: $FFFFF420
15 14 13 12
PU7 PU6 PU5 PU4
Address: $FFFFF422
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 (output), D[7:0] controls the data to the pins.
While the DIRECTION bits are low (input), D[7:0] reports the signal level on the pins. The
data bits may be written at any time. Bits that are configured as inputs will accept the data
but the written data will not be accessible until their respective pins are configured as out-
7-8 MC68328 DRAGONBALL PROCESSOR USER'S MANUAL
Table 7-2. Port E Bit Functions
Bit Port Function Other Function
0
1
2
3
4
5
6
7
11 10 9
DIR3 DIR2 DIR1
Figure 7-14. Port E Data/Direction Register
11 10 9
PULLUP
PU3 PU2 PU1
Figure 7-15. Port E Select Register
none none
Bit 1 CSA1
Bit 2 CSA2
Bit 3 CSA3
Bit 4 CSB0
Bit 5 CSB1
Bit 6 CSB2
Bit 7 CSB3
8 7 6 5
DIR0 D7 D6 D5
8 7 6 5
PU0 SEL7 SEL6 SEL5
4 3 2 1
DATA
D4 D3 D2 D1
Reset Value: $0000
4 3 2 1
SELECT
SEL4 SEL3 SEL2 SEL1
Reset Value: $8080
MOTOROLA
0
D0
0
SEL0