38C3 datasheet(115/224 Pages) RENESAS

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2-50

38C3 Group User’s Manual

APPLICATION

2.3 Serial I/O

q Control in the slave unit

After setting the relevant registers as shown in Figure 2.3.23, the slave unit becomes the state

where a synchronous clock can be received at any time, and the serial I/O interrupt occurs each

time an 8-bit synchronous clock is received.

In the serial I/O interrupt processing routine, the data to be transmitted next is written to the serial

I/O register after the received data is read out.

However, if no serial I/O interrupt occurs for a certain time (heading adjustment time or more), the

following processing will be performed.

1. The first 1-byte data of the transmission data in the block is written into the serial I/O register.

2. The data to be received next is processed as the first 1 byte of the received data in the block.

Figure 2.3.25 shows a control procedure of the slave unit using the serial I/O interrupt and any

timer interrupt (for heading adjustment).

Fig. 2.3.25 Control procedure of slave unit

Write a transmission data

Read a reception data

Within a block transfer

term?

A received byte

counter

≥ 8?

RTI

Write dummy data (FF16)

A received byte counter +1

Heading

adjustment

counter

Initial

value

(Note 3)

Serial I/O reception interrupt

processing routine

Timer interrupt processing

routine

Heading adjustment

counter – 1

Heading adjustment

counter = 0?

RTI

Write the first transmission

data (first byte) in a block

A received byte counter

Confirmation of the received

byte counter to judge the

block transfer term

In this example, set the value which is equal to the

heading adjustment time divided by the timer interrupt

cycle as the initial value of the heading adjustment

counter.

For example: When the heading adjustment time is 8 ms

and the timer interrupt cycle is 1 ms, set

8 as the initial value.

CLT (Note 1)

CLD (Note 2)

Push register to stack

Pushing the register used in

the interrupt processing

routine into the stack

CLT (Note 1)

CLD (Note 2)

Push register to stack

Pushing the register used

in the interrupt processing

routine into the stack.

Pop registers

Popping registers which is

pushed to stack

Pop registers

Popping registers which is

pushed to stack

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

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

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