Electronics America Single-Chip Microcontrollers User's Manual

CHAPTER 4 PORT FUNCTIONS

User’s Manual U15331EJ4V1UD 79

4.2.3 Port 2

This is a 6-bit I/O port with an output latch. Port 2 can be specified in the input or output mode in 1-bit units by

using port mode register 2 (PM2). When using the P20 to P25 pins as input port pins, on-chip pull-up resistors can be

connected in 1-bit units by using pull-up resistor option register B2 (PUB2).

This port is also used for serial interface I/O.

RESET input sets this port to input mode.

Figures 4-4 to 4-8 show block diagrams of port 2.

Caution When using the pins of port 2 as the serial interface, the I/O or output latch must be set

according to the function to be used. For how to set the latches, see Table 11-2 Serial Interface

20 Operation Mode Settings and 12.3 (1) Serial operation mode register 1A0 (CSIM1A0).

Figure 4-4. Block Diagram of P20

Internal bus

P-ch

P20/ASCK20/

SCK20

PUB2

PORT

PUB20

Alternate

function

Output latch

(P20)

PM20

Alternate

function

Selector

PUB2: Pull-up resistor option register B2

PM: Port mode register

RD: Port 2 read signal

WR: Port 2 write signal