ER-A770 (serv.man7). Internal 2 Line Display - Sharp EPOS Service Manual (repair manual). Page 5

Host 

 CKDC9 in the UP-I16DP PWB

Set the data "A" in the shift register of the host POS.

Send the data "A" to the UP-I16DP with shift clock added to the
HOST and read the data on the UP-I16DP.

Set the data "B" to the HOST.

Send the data "B" to the UP-I16DP with shift clock’s added by the
HOST. Then, sen the previous data "A" in the UP-I16DP to the
HOST.

The host cash register transfers data to UP-I16DP after eigth shift
clocks. In this event, the contents of the UP-I16DP shift register
(data A) is not destroyed.

The HOST checks if the returned data "A" are properly transmit-
ted. The data "B" returns to the HOST to be checked after a next
data or a dummy data are sent.

Set the data "A" in the CKDC9 side shift register.

Sent the data "A" on the shift clock and read it on the host side.

Set the dame data "A" in the CKDC9 side shift register.

Again, sent the data "A" on the shift clock.

On the host side, compare the data "A" read in 

 to check if the

transmission was achieved properly.

The /SHEN2A signal is used to check lock up of the UP-I16DP.
Normally, it will complete within 2msec before /SHEN2A is set after
the HOST completed data transmission. If /SHEN2A was not received
within the predetermined time, it will be error processed as an error.

CKDC9

OUT

IN

OUT

IN

HTS2A

STH2A

/SCK2A

Host

Shift register

UP-I16DP

HOST

UP-I16DP

A

Unpredicatable

HOST

UP-I16DP

A

HOST

UP-I16DP

A

B

HOST

UP-I16DP

A

A

B

B

HOST

A

Unpredicatable

CKDC9

A

HOST

CKDC9

A

HOST

CKDC9

A

HOST

CKDC9

/SHEN2A

/SCK2A

30µs ~ 2ms