HD66712 Datasheet, PDF (41/88 Pages) Hitachi Semiconductor – Dot-Matrix Liquid Crystal Display Controller/Driver

HD66712U
Instructions
Outline
Only the instruction register (IR) and the data register (DR) of the HD66712 can be controlled by the
MPU. Before starting internal operation of the HD66712, control information is temporarily stored in
these registers to allow interfacing with various MPUs, which operate at different speeds, or various
: ^{peripheral control devices. The internal operation of the HD66712 is determined by signals sent from the}
MPU. These signals, which include register selection (RS), read/write (R/ ), and the data bus (DB0 to
DB7), make up the HD66712 instructions (Table 12). There are four categories of instructions that:
• Designate HD66712 functions, such as display format, data length, etc.
• Set internal RAM addresses
• Perform data transfer with internal RAM
• Perform miscellaneous functions
Normally, instructions that perform data transfer with internal RAM are used the most. However, auto-
incrementation by 1 (or auto-decrementation by 1) of internal HD66712 RAM addresses after each data
write can lighten the program load of the MPU. Since the display shift instruction (Table 10) can perform
concurrently with display data write, the user can minimize system development time with maximum
programming efficiency.
When an instruction is being executed for internal operation, no instruction other than the busy
flag/address read instruction can be executed.
Because the busy flag is set to 1 while an instruction is being executed, check it to make sure it is 0
before sending another instruction from the MPU.
Note:
Be sure the HD66712 is not in the busy state (BF = 1) before sending an instruction from the
MPU to the HD66712. If an instruction is sent without checking the busy flag, the time between
the first instruction and next instruction will take much longer than the instruction time itself.
Refer to Table 12 for the list of each instruction execution time.
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