NEC mPD789101, User Manual

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CHAPTER 5 PORT FUNCTIONS
User’s Manual U13045EJ2V0UM00
75
5.2 Port Configuration
A port consists of the following hardware.
Table 5-2. Configuration of Port
Parameter Configuration
Control register Port mode register (PMm: m = 0 to 2, 5)
Pull-up resistor option register 0 (PU0)
Pull-up option register B2 (PUB2)
Port Total: 20 (input: 7, input/output: 16)
Pull-up resistor • Mask ROM versions
Total: 16 (software control: 12, mask option specification: 4)
• Flash memory versions
Total: 12 (software control only)
5.2.1 Port 0
This is a 4-bit I/O port with output latches. Port 0 can be specified as input or output mode in 1-bit units by using
port mode register 0 (PM0). When pins P00 to P03 are used as input port pins, on-chip pull-up resistors can be
connected in 4-bit units by using pull-up resistor option register 0 (PU0).
RESET input sets port 0 to input mode.
Figure 5-2 shows the block diagram of port 0.
Figure 5-2. Block Diagram of P00 to P03
PU0: Pull-up resistor option register 0
PM: Port mode register
RD: Port 0 read signal
WR: Port 0 write signal
Internal bus
WR
PU0
RD
WR
PORT
WR
PM
PU00
Output latch
(P00 to P03)
PM00 to PM03
V
DD
P-ch
P00 to P03
Selector