38C3 datasheet(114/224 Pages) RENESAS

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38C3 Group User’s Manual

APPLICATION

2-49

2.3 Serial I/O

Control procedure by software:

q Control in the master unit

After setting the relevant registers shown in Figure 2.3.22, the master unit starts transmission or

reception of 1-byte data by writing transmission data to the serial I/O register.

To perform the communication in the timing shown in Figure 2.3.21, take the timing into account

and write transmission data. Additionally, read out the reception data when the serial I/O interrupt

request bit is set to “1,” or before the next transmission data is written to the serial I/O register.

Figure 2.3.24 shows a control procedure of the master unit using timer interrupts.

Fig. 2.3.24 Control procedure of master unit

Interrupt processing routine

executed every 488

µs

Write a transmission data

Read a reception data

Within a block transfer

period?

Complete to transfer

a block?

RTI

Write the first transmission data

(first byte) in a block

Count a block interval counter

Start a block transfer?

Generating a certain block interval by

using a timer or other functions

Check of the block interval counter and

determination to start a block transfer

CLT (Note 1)

CLD (Note 2)

Push register to stack

Note 1: When using the Index X mode flag (T).

Note 2: When using the Decimal mode flag (D).

Pushing the register used in the interrupt

processing routine into the stack

Pop registersPopping registers which is pushed to stack

38C3 Datasheet(PDF) 114 Page - Renesas Technology Corp