uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM
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4.2 Port Configuration<br />
56<br />
A port consists of the following hardware.<br />
CHAPTER 4 PORT FUNCTIONS<br />
Table 4-2. Configuration of Port<br />
Parameter Configuration<br />
Control register Port mode register (PMm: m = 0 to 2)<br />
Pull-up resistor option register 0 (PU0)<br />
Pull-up option register B2 (PUB2)<br />
Port Total: 33<br />
CMOS I/O: 17<br />
P-ch open-drain I/O: 8<br />
P-ch open-drain output: 8<br />
Pull-up resistor 17 (software control)<br />
Pull-down resistor • Mask ROM versions: 16 (8 of these can be specified by the mask option)<br />
• Flash memory versions: None<br />
4.2.1 Port 0<br />
This is a 8-bit I/O port with output latches. Port 0 can be specified as input or output mode in 1-bit units by using<br />
port mode register 0 (PM0). When pins P00 to P07 are used as input port pins, on-chip pull-up resistors can be<br />
connected in 8-bit units by using pull-up resistor option register 0 (PU0).<br />
RESET input sets port 0 to input mode.<br />
Figure 4-2 shows the block diagram of port 0.<br />
Internal bus<br />
WRPU0<br />
RD<br />
WRPORT<br />
WRPM<br />
PU0: Pull-up resistor option register 0<br />
PM: Port mode register<br />
RD: Port 0 read signal<br />
WR: Port 0 write signal<br />
Figure 4-2. Block Diagram of P00 to P07<br />
PU00<br />
Output latch<br />
(P00 to P07)<br />
PM00 to PM07<br />
Selector<br />
Preliminary User’s Manual U14938EJ1V0UM<br />
VDD0<br />
P-ch<br />
P00 to P07