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7480 Group and 7481 Group User's Manual

2-12

APPLICATIONS

2.2.5 Application Example of Pulse Width Measurement Mode

Communications between Two Microcomputers (Reception)

POINT: 8-bit data is received by measuring each bit’s HIGH-level width input to the CNTR pin and

identifying each bit data.

SPECIFICATIONS:

Clock: f(XIN) = 8 MHz

The HIGH-level width of CNTR0 pin input is measured using the pulse width

measurement mode of timer X.

• Count source: f(XIN)/8

The start, stop bits and each bit data of 8-bit receive data are identified by the

measured values of the HIGH-level widths.

Figure 2.2.11 shows a peripheral circuit example.

Figure 2.2.12 shows a communication format example.

Figure 2.2.13 shows a communication control procedure example.

2.2 Timer X and Timer Y

Figure 2.2.12 Communication Format Example

Figure 2.2.11 Peripheral Circuit Example

D0=0

D1=1

D7=1

D2=0

Start

pulse

0.15 ms

0.35 ms

0.55 ms

0.75 ms

0.15 ms

0.35 ms

0.05 ms

8-bit data

Longest communication time

≈ 4.6 ms

Shortest communication time

≈ 3.0 ms

Data pulse‘0’: HIGH level output for 0.15 ms

Data pulse‘1’: HIGH level output for 0.35 ms

Start pulse: HIGH level output for 0.55 ms

Stop pulse: HIGH level output for 0.75 ms

(The LOW levels are output for 0.05 ms or more before

and after each pulse.)

Stop

pulse

Microcomputer (tr

t er)

7480 Group

7481 Group

(Receiver)

P40/CNTR0

Data

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