Port C - Motorola DragonBall MC68328 User Manual

15 14 13
0 0 0
Address: $FFFFF40A
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 outputs. 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 while the SELECT bits are low.
SELECT- SEL[7:0]
These bits select whether CPU data-bus low byte or I/O port signals are connected to the
pins. While high, the port I/O function is connected to the pin. While low, the D7-D0 func-
tions are connected.

7.1.4 Port C

Port C is multiplexed with various 68000 bus-control signals that are identified below.
All 8 bits are implemented in the registers, but only 6 bits connect to the outside. As with other
ports, each bit can be individually configured. Bit 0 can be used only when the on-chip PLL
is selected because the MOCLK function is needed to disable the PLL. The on-chip PLL will
be selected when this bit serves as a port I/O. The programmer's model for port C follows.
15 14 13
DIR7 DIR6 DIR5 DIR4
Address: $FFFFF410
MOTOROLA MC68328 DRAGONBALL PROCESSOR USER'S MANUAL
12 11 10 9
UNUSED
0 0 0 0
Figure 7-7. Port B Select Register
Table 7-1. Port C Bit Functions
Bit
0
1
2
3
4
5
6
7
12 11 10 9
DIRECTION
DIR3 DIR2 DIR1
Figure 7-8. Port C Data/Direction Register
8 7 6 5
0 SEL7 SEL6 SEL5
Port Function Other Function
Bit 0 MOCLK
UDS
Bit 1
LDS
Bit 2
none none
Bit 4 NMI
Bit 5 DTACK
Bit 6 WE (PCMCIA)
none none
8 7 6 5
DIR0 D7 D6 D5
Parallel Ports
4 3 2 1
SELECT
SEL4 SEL3 SEL2 SEL1
Reset Value: $0000
4 3 2 1
DATA
D4 D3 D2 D1
Reset Value: $0000
0
SEL0
0
D0
7-5