Motorola MC68VZ328 用户手册
Programming Model
I/O Ports
10-37
10.4.11
Port M Registers
Port M is composed of the following four general-purpose I/O registers:
•
Port M direction register (PMDIR)
•
Port M data register (PMDATA)
•
Port M pull-up enable register (PMPUEN)
•
Port M select register (PMSEL)
Each signal in the PMDATA register connects to an external pin. It should be noted that pins 6 and 7 are
not connected to external pins.
not connected to external pins.
10.4.11.1
Port M Direction Register
The direction register controls the direction (input or output) of the line associated with the PMDATA bit
position. When the data bit is assigned to a dedicated I/O function by the PMSEL register, the DIR bits are
ignored. The settings for the PMDIR register bit positions are shown in Table 10-51.
position. When the data bit is assigned to a dedicated I/O function by the PMSEL register, the DIR bits are
ignored. The settings for the PMDIR register bit positions are shown in Table 10-51.
PMDIR
Port M Direction Register
0x(FF)FFF448
BIT 7
6
5
4
3
2
1
BIT 0
DIR5
DIR4
DIR3
DIR2
DIR1
DIR0
TYPE
rw
rw
rw
rw
rw
rw
RESET
0
0
0
0
0
0
0
0
0x00
Table 10-51. Port M Direction Register Description
Name Description
Setting
Reserved
Bits
Bits
7–6
Reserved
These bits are reserved and should be set to
0.
0.
DIRx
Bits 5–0
Bits 5–0
Direction—These bits control the direction of
the pins in an 8-bit system. They reset to 0.
the pins in an 8-bit system. They reset to 0.
0 = The pins are inputs.
1 = The pins are outputs.
1 = The pins are outputs.