Nec switch Uživatelský manuál stáhnout pdf (Strana 60)

CHAPTER 4 PORT FUNCTIONS

User’s Manual U12978EJ3V0UD

4.2.1 Port 0

This is an 8-bit I/O port with an output latch. Port 0 can be specified in the input or output mode in 1-bit units by

using port mode register 0 (PM0). When the P00 to P07 pins are used as input port pins, on-chip pull-up resistors

can be connected in 8-bit units by using pull-up resistor option register 0 (PU0). CMOS output or N-ch open-drain

output can also be specified in 8-bit unit by using port output mode register 0 (POM0).

Port 0 is set in the input mode when the RESET signal is input.

Figure 4-2 shows a block diagram of port 0.

Figure 4-2. Block Diagram of P00 to P07

DD0

P00 to P07

PU0

PORT

Output latch

(P00 to P07)

PM00 to PM07

PU00

P-ch

N-ch

DD0

POM00

Internal bus

Selector

POM0

POM0: Port output mode register 0

PU0: Pull-up resistor option register 0

PM: Port mode register

RD: Port 0 read signal

WR: Port 0 write signal

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Nec switch Uživatelský manuál Strana 60