Single-Chip Microcontrollers User's Manual

145
CHAPTER 6 PORT FUNCTIONS
6.2.7 Port 5
Port 5 is an 8-bit input/output port with output latch. P50 to P57 pins can specify the input mode/output mode in
1-bit units with the port mode register 5 (PM5). When P50 to P57 pins are used as input ports, an on-chip pull-up
resistor can be connected to them in 8-bit units with a pull-up resistor option register L (PUOL).
Port 5 can drive LEDs directly.
Dual-functions include address bus function in external memory expansion mode.
RESET input sets port 5 to input mode.
Figure 6-12 shows a block diagram of port 5.
Figure 6-12. Block Diagram of P50 to P57
PUO : Pull-up resistor option register
PM : Port mode register
RD : Port 5 read signal
WR : Port 5 write signal
P-ch
WR PM
WR PORT
RD
WR
PUO
V DD
Selector
PUO5
Output Latch
(P50 to P57)
PM50 to PM57
Internal bus
P50/A8 to
P57/A15