TMP86CS44UG datasheet(62/172 Pages) TOSHIBA

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Page 52

5. I/O Ports

TMP86CS44UG

5.5 Port P4 (P47 to P40)

Port P4 is an 8-bit input/output port which can be configured as an input or an output in one-bit unit under software

control. Input/output mode is specified by the corresponding bit in the port P4 input/output control register (P4CR).

Port P4 is configured as an input if its corresponding P4CR bit is cleared to “0”, and as an output if its corresponding

P4CR bit is set to “1”.

During reset, the P4CR is initialized to “0” and port P4 is input mode. The P4 output latches are also initialized to

“0”.

When used as an input port, the corresponding bit of P4CR is cleared to “0”.

When used as an output port, the corresponding bit of P4CR is set to “1”. Data can be written into the output latch

regardless of P4CR contents, therefore initial output data should be written into the output latch before setting P4CR.

Figure 5-6 Port P4

Note: Ports set to the input mode read the pin states. Ports set to the output mode read the output latch. When input pin and out-

put pin exist in port P4 together, the contents of the output latch which is specified as an input mode may be rewritten by

executing the bit manipulation instructions.

P4DR

(0004H)

R/W

543

P47

P46

P45

P44

P43

P42

P41

P40

(Initial value: 0000 0000)

P4CR

(000FH)

543

(Initial value: 0000 0000)

P4CR

I/O control for port P4 (Speci-

fied for each bit)

0: Input mode

1: Output mode

R/W

Output latch

Data input (P4DR)

Data output

STOP

OUTEN

P4CRi

P4CRi input

P4i

Note:i=7

to 0

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