HD66712 Datasheet, PDF (36/88 Pages) Hitachi Semiconductor – Dot-Matrix Liquid Crystal Display Controller/Driver

HD66712U
Interfacing to the MPU
The HD66712 can send data in either two 4-bit operations or one 8-bit operation, thus allowing
interfacing with 4- or 8-bit MPUs.
• For 4-bit interface data, only four bus lines (DB4 to DB7) are used for transfer. Bus lines DB0 to DB3
are disabled. The data transfer between the HD66712 and the MPU is completed after the 4-bit data
has been transferred twice. As for the order of data transfer, the four high order bits (for 8-bit
operation, DB4 to DB7) are transferred before the four low order bits (for 8-bit operation, DB0 to
DB3).
The busy flag must be checked (one instruction) after the 4-bit data has been transferred twice. Two
more 4-bit operations then transfer the busy flag and address counter data.
• For 8-bit interface data, all eight bus lines (DB0 to DB7) are used.
• When the IM pin is low, the HD66712 uses a serial interface. See “Transferring Serial Data.”
RS
R/W
E
DB7
IR7
IR3
BF
AC3
DR7
DR3
DB6
IR6
IR2
AC6
AC2
DR6
DR2
DB5
IR5
IR1
AC5
AC1
DR5
DR1
DB4
IR4
IR0
AC4
AC0
DR4
DR0
Instruction register (IR)
write
Busy flag (BF) and
address counter (AC)
read
Data register (DR)
read
Figure 13 4-Bit Transfer Example
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