DESCRIPTION
7902 Group User’s Manual
1-6
1.3 Pin description
I/O port P0
I/O port P1
I/O port P2
I/O port P3
Name
P00–P07
A16–A23
P10–P17
D0–D7,
LA0–LA7
P20–P27
P20/D8–
P27/D15
P30–P33
P30,
RDY,
RD,
BLW,
BHW
Pin
Table 1.3.2 Pin description (2)
I/O
Output
I/O
I/O,
Input,
Output,
Output
Input/Output
Function
[Single-chip mode]
P0 is an 8-bit CMOS I/O port and has an I/O direction register.
Each pin can function as an input or output port pin.
[Memory expansion mode][Microprocessor mode]
High-order 8 bits (A16–A23) of an address are output.
By software, these pins can function as an I/O port with the
same function as port P0.
[Single-chip mode]
P1 is an 8-bit I/O port with the same function as port P0.
[Memory expansion mode][Microprocessor mode]
Low-order 8 bits (D0–D7) of data are input or output.
When area CS2 is accessed with the external data bus width
= 8 bits, by software, address (LA0–LA7) output and data
(D0–D7) input/output can be performed with the time-sharing method.
[Single-chip mode]
P2 is an 8-bit I/O port with the same function as port P0.
[Memory expansion mode][Microprocessor mode]
sWhen the external data bus width = 8 bits (BYTE = Vcc level)
P2 is an 8-bit I/O port with the same function as port P0.
sWhen the external data bus width = 16 bits (BYTE = Vss level)
High-order 8 bits (D8–D15) of data are input and output.
[Single-chip mode]
P3 is a 4-bit I/O port with the same function as port P0.
[Memory expansion mode][Microprocessor mode]
sWhen MD1 = Vss level, MD0 = Vss level
P30 functions as an I/O port pin with the same function as port P0.
By software, P30 can function as pin RDY.
sWhen MD1 = Vss level, MD0 = Vcc level
P30 functions as pin RDY. By software, P30 can function as
an I/O port with the same function as port P0.
While pin RDY’s input level = “L,” the microcomputer is placed
in Ready state.
P31, P32, and P33 become pins RD, BLW, and BHW, respectively.
The microcomputer reads data or instruction codes while
pin RD’s level = “L.”
sWhen the external data bus width = 8 bits (BYTE = Vcc level)
The microcomputer writes data when pin BLW’s level =
“L.” Pin BHW functions as an I/O port pin (P33), with the
same function as port P0.
sWhen the external data bus width = 16 bits (BYTE = Vss level)
The microcomputer writes data into an even-numbered
address while pin BLW’s level = “L.” The microcomputer
writes data into an odd-numbered address when pin BHW’s
evel = “L.”