7220 datasheet(73/303 Pages) RENESAS

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2-46

7220 Group User’s Manual

FUNCTIONAL DESCRIPTION

2.7 Serial I/O

The transmit side in Figure 2.7.7, P21 is set as the serial I/O data output pin and P20 is set as the serial

I/O synchronous clock output pin by the initialization program.

The receive side, P21 is set as the serial I/O data input pin and P20 is used for the serial I/O synchronous

clock (external clock) input pin by the initialization program.

Figure 2.7.8 shows the serial data transmit/receive processing sequence using the above structure.

Fig. 2.7.7 Connection example for serial I/O transmit/receive

As a result of the above processing 1-byte data is transferred from the transmit side to the receive side.

When the transmit operation is completed, interrupts occur on both sides, so that completion of the data

transfer can be reported.

After that, repeating the processing after the symbol (w) can transmit/receive more data.

Transmit side

LDM

#$0C, $DC

; Set serial I/O mode register.

CLB

2, $FD

; Reset serial I/O interrupt

request bit.

SEB

2, $FF

; Set the serial I/O interrupt

enable bit to “1.”

LDM

#DATA, $DD ; Write transfer data to serial

I/O register.

Fig. 2.7.8 Serial data transmit/receive processing sequence

Receive side

LDM

#$48, $DC

; Set serial I/O mode

CLB

2, $FD

; Reset serial I/O interrupt

request bit.

SEB

2, $FF

; Set serial I/O interrupt

enable bit to “1.”

wLDM

#$FF, $DD

; Write dummy data to

serial I/O register.

Serial I/O Mode Register

Serial data

P21/SOUT

SOUT/P21

P20/SCLK

SCLK/P20

Synchronous clock

Transmit Side

Receive Side

Serial I/O Mode Register

M37221M6-XXXSP/FP

1: SCLK, SOUT

Internal synchronous clock selection bits

Serial I/O port selection bit

Fix this bit to “0.”

Transfer direction selection bit

Serial input pin selection bit

Nothig is assigned.

Synchronous clock selection bit

1: Internal clock

1: SCLK, SOUT

0: External clock

1: Input signal from SOUT pin

Internal synchronious clock selection bits

Serial I/O port selection bit

Fix this bit to “0.”

Transfer direction selection bit

Serial input pin selection bit

Nothig is assigned.

Synchronous clock selection bit

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