38C3 datasheet(111/224 Pages) RENESAS

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2-46

38C3 Group User’s Manual

APPLICATION

2.3 Serial I/O

(3)

Cyclic transmission or reception of block data (data of specified number of bytes) between

two microcomputers

Outline : When the clock synchronous serial I/O is used for communication, synchronization of the

clock and the data between the transmitting and receiving sides may be lost because of

noise included in the synchronous clock. It is necessary to correct that constantly, using

“heading adjustment”.

This “heading adjustment” is carried out by using the interval between blocks in this

example.

Figure 2.3.20 shows a connection diagram.

Fig. 2.3.20 Connection diagram

Specifications: • Synchronous clock frequency : 131 kHz (f(XIN) = 4.19 MHz is divided by 32.)

• Byte cycle: 488

µs

• Number of bytes for transmission or reception : 8 bytes/block each

• Block transfer cycle : 16 ms

• Block transfer term : 3.5 ms

• Interval between blocks : 12.5 ms

• Heading adjustment time : 8 ms

• Transfer direction : LSB first

Limitations of the specifications:

• Reading of the reception data and setting of the next transmission data must be

completed within the time obtained from “byte cycle – time for transferring 1-byte

data” (in this example, the time taken from generating of the serial I/O interrupt

request to input of the next synchronous clock is 431

µs).

• “Heading adjustment time < interval between blocks” must be satisfied.

SCLK1

SIN

SOUT

38C3 group

(master side)

38C3 group

(slave side)

SCLK1

SOUT

SIN

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