NEC UPD789026 Series, User Manual

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CHAPTER 4 PORT FUNCTIONS
User's Manual U11919EJ3V0UM00
71
4.2 Port Configuration
Ports have the following hardware configuration.
Table 4-2. Port Configuration
Parameter Configuration
Control register Port mode register (PMm: m = 0 to 5)
Pull-up resistor option register (PUO)
Port Total: 34 (input/output: 34)
Pull-up resistor Total: 34 (on-chip pull-up resistor can be connected by software)
4.2.1 Port 0
This is an 8-bit I/O port with output latch. Port 0 can be specified in the input or output mode in 1-bit units by
using the port mode register 0 (PM0). When using P00 to P07 pins as input port pins, on-chip pull-up resistors can
be connected in 8-bit units by using the pull-up resistor option register (PUO).
RESET input sets port 0 to input mode.
Figure 4-2 shows the block diagram of port 0.
Figure 4-2. Block Diagram of P00 to P07
Internal Bus
WR
PUO
RD
WR
PORT
WR
PM
Output Latch
(P00 to P07)
PM00 to PM07
Selector
PUO0
V
DD0
P-ch
P00 to P07
PUO : Pull-up resistor option register
PM : Port mode register
RD : Port 0 read signal
WR : Port 0 write signal
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