User's Manual

142

µPD750008 USER'S MANUAL

(6) Transfer start

Serial transfer is started by writing transfer data into shift register (SIO), provided that the following two

conditions are satisfied:

• The serial interface operation enable/disable specification bit (CSIE) is set to 1.

• The internal serial clock is not operating after 8-bit serial transfer, or SCK is high.

Caution Setting CSIE after writing data to the shift register does not start transfer.

When eight bits have been transferred, serial transfer automatically terminates setting the interrupt request

flag (IRQCSI).

Example To transfer the RAM data specified with the HL register to SIO, load the SIO data to the

accumulator and start serial transfer:

MOV XA,@HL ; Fetch transmit data from RAM

SEL MB15 ; or CLR1 MBE

XCH XA,SIO ; Exchange transmit data and receive data, and start transfer

(7) Application of the three-wire serial I/O mode

(a) Data is transferred starting with the MSB on a transfer clock of 262 kHz (during 4.19-MHz

operation). (Master operation)

CLR1 MBE

MOV XA,#10000010B

MOV CSIM,XA ; Set transfer mode

MOV XA,TDATA ; TDATA is transfer data storage address

MOV SIO,XA ; Set transfer data, and start transfer

Caution A second or subsequent transfer can be started by setting data in SIO (MOV SIO,XA

or XCH XA,SIO).

In this case, the SI/SBI pin on the µPD750008 can be used as an input.

SCK

µPD750008

SO/SB0

SCK

µPD7225G (LCD controller/driver), etc.