TMP86CS44UG datasheet(57/172 Pages) TOSHIBA

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Page 47

TMP86CS44UG

5. I/O Ports

The TMP86CS44UG has 5 parallel input/output ports (35 pins) as follows.

Each output port contains a latch, which holds the output data. All input ports do not have latches, so the external

input data should be externally held until the input data is read from outside or reading should be performed several

times before processing. Figure 5-1 shows input/output timing examples.

External data is read from an I/O port in the S1 state of the read cycle during execution of the read instruction.

This timing cannot be recognized from outside, so that transient input such as chattering must be processed by the

program.

Output data changes in the S2 state of the write cycle during execution of the instruction which writes to an I/O

port.

Note: The positions of the read and write cycles may vary, depending on the instruction.

Figure 5-1 Input/Output Timing (Example)

Primary Function

Secondary Functions

Port P0

8-bit I/O port

External interrupt input, serial and timer/counter input/output

Port P1

8-bit I/O port

External interrupt input, timer/counter input/output, and divider output

Port P2

3-bit I/O port

External interrupt input, and STOP mode release signal input

Port P3

8-bit I/O port

Analog input, and STOP mode release signal input

Port P4

8-bit I/O port

Instruction

execution cycle

Input strobe

Data input

Ex: LD A, (x)

Fetch cycle

Read cycle

S0 S1 S2 S3 S0 S1 S2 S3 S0 S1 S2 S3

Instruction

execution cycle

Output strobe

Data output

Ex: LD (x), A

Fetch cycle

Write cycle

S0 S1 S2 S3 S0 S1 S2 S3 S0 S1 S2 S3

(a) Input timing

(b) Output timing

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