Casio CE-3700, Service Manual

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[ Data reading procedure ]
When the CPU read the data of EEPROM, CPU send the CS signal and SK signal to EEPROM.
Then CPU send the address to EEPROM, and then EEPROM return the data to CPU.
[ Data writing procedure ]
When the CPU save the data to EEPROM, CPU sends the CS and SK signal to EEPROM.
And CPU send the address and data to EEPROM from pin No. 15.
When the EEPROM writes the data, EEPROM outputs the busy signal form DO terminal to CPU.
After finish writing, EEPROM outputs the ready signal from DO terminal to CPU.
CS
SK
DI
DO
Address
Data
Output data here
CS
SK
DI
DO
Status
READY(H)
BUSY(L)
Data Address
High Impedance