3819 datasheet(42/218 Pages) RENESAS

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3819 Group

SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER

MITSUBISHI MICROCOMPUTERS

q Setting of Serial I/O Automatic Transfer

Timing

The timing of serial I/O automatic transfer is set with the serial

I/O1 control register (address 001916) and the serial I/O auto-

matic transfer interval register (address 001C16).

The serial I/O1 control register sets the transfer clock speed,

and the serial I/O automatic transfer interval register sets the

serial I/O automatic transfer interval. This setting of transfer in-

terval is valid only when selecting the internal clock as the

clock source.

q Start of Serial I/O Automatic Transfer

Automatic transfer mode is set by writing “1” to the bit 0 of the

serial I/O automatic transfer control register (address 001A16),

then automatic transfer starts by writing “1” to the bit 1.

The bit 1 of the serial I/O automatic transfer control register is

always “1” during automatic transfer; writing “0” can complete

the serial I/O automatic transfer.

q Operation in Serial I/O Automatic Transfer

Modes

There are two modes for serial I/O automatic transfer: full du-

plex mode and transmit-only mode. Either internal or external

clock can be selected for each of these modes.

(2.1) Operation in Full Duplex Mode

In full duplex mode, data can be transmitted and received at the

same time. Data in the automatic transfer RAM is transmitted in

sequence in accordance with the serial I/O automatic transfer data

pointer and simultaneously reception data is written to the auto-

matic transfer RAM.

The transfer timing of each bit is the same as that in ordinary op-

eration mode, and the transfer clock stops at “H” after eight

transfer clocks are counted.

When selecting the internal clock, the transfer clock remains at “H”

for the time set with the serial I/O automatic transfer interval regis-

ter, then the data at the next address (the address is indicated with

the serial I/O automatic transfer data pointer) are transferred.

If when selecting the external clock, the setting of the automatic

transfer interval register is invalid, so control the transfer clock ex-

ternally.

The last data transfer completes when the contents of the serial

I/O automatic transfer pointer reach “0016”. At that point, the serial

I/O automatic transfer interrupt request bit is set to “1” and the bit

1 of the serial I/O automatic transfer control register is cleared to

“0” to complete the serial I/O automatic transfer.

(2.2) Operation in Transmit-Only Mode

The operation in transmit-only mode is the same as that in full du-

plex mode, except for that data is not transferred from the serial

I/O1 register to the serial I/O automatic transfer RAM.

Fig. 19 Serial I/O1 register transfer operation in full duplex mode

•

DO7

DO6

DO5 DO4

DO3

DO2 DO1

DO0

Transfer clock

DI1

DI0

DO7

DO6

DO5

DO4

DO3

DO2

DI2

DI1

DI7

DI6

DI5

DI4

DI3

DI2

DI1

DI0

DO7

DO6

DO5

DO4

DO3

DO7

DO6

DO5

DO4

DO3

DO2

DO1

DI0

Transfer direction selection bit

LSB first (SC15 = “0” ) : MSB

MSB first (SC15 = “1” ) : LSB

LSB

MSB

SOUT

SIN

Serial I/O1 register

DI0

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