Computer Hardware User's Manual

TMP92CM22

2007-02-16

92CM22-54

3.5.2 Port 4 (P40 to P47)

Port 4 is an 8-bit general-purpose I/O port*. Bits can be individually set as either inputs

or outputs by control register P4CR and function register P4FC*.

In addition to functioning as a general-purpose I/O port, port 4 can also function as a

address bus (A0 to A7).

After released reset, device set Port 4 to pins of follow function by combination of AM1

and AM0 pins.

AM1 AM0 Function Setting after Reset

0 0 Don’t use this setting

0 1 Address bus (A0 to A7)

1 0 Address bus (A0 to A7)

1 1 Don’t use this setting

*: When these ports are used as general-purpose I/O port, each bit can be set individually for input or output. However, each

bit cannot be set individually for input or output even if 1bit or more bits are used as address bus in same port.

All of general-purpose I/O ports except for port that used as address bus are operated as output port.

Please be careful when using this setting.

Figure 3.5.3 Port 4

Internal data bus

Direction control

(on bit basis)*

Reset

P4CR write

Output latch

P4 write

Selector

P4 read

Port 4

P40 to P47

(A0 to A7)

Function control

(on bit basis)

P4FC write

Output buffer

Internal address bus

0 to A7