3819 datasheet(115/218 Pages) RENESAS

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2. APPLICATION

MITSUBISHI MICROCOMPUTER

3819 Group

2.3 Serial I/O

3819 Group USER’S MANUAL

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

[without using an automatic transfer]

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

data between the transmitter and receiver sides may be lost because of noise included in the

synchronizing clock. Thus, it is necessary to be corrected constantly. This “heading adjustment” is carried

out by using the interval between blocks in this example.

Fig. 2.3.23 Connection diagram [Cyclic transmission or reception of block data between microcomputers]

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 : each 8 byte/block

• Block transmission cycle : 16 ms

• Block transmission period : 3.5 ms

• Interval between blocks : 12.5 ms

• Heading adjustive time : 8 ms

• Transmission direction : LSB first

Limitations of the specifications

1. Reading of the reception data and setting of the next transmission data must be completed within the time

obtained from “byte cycle – time for transmitting 1-byte data” (in this example, the time taken from generating

of the Serial I/O 1 interrupt request to generating of the next synchronizing clock is 431

µs).

2. “Heading adjustive time < interval between blocks” must be satisfied.

3. Although the transmission direction can be switched for the Serial I/O of 3819 group, it cannot be

switched for some serial I/Os of 740 family including 38000 series (only LSB first). Be sure to check when

deciding specifications.

SCLK

SIN

SOUT

Master unit

SCLK

SIN

SOUT

Slave unit

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