HD66727 Datasheet, PDF (29/97 Pages) Hitachi Semiconductor – Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver with Key Scan Function

HD66727
Instructions
Outline
Only the instruction register (IR) and the data register (DR) of the HD66727 can be controlled by the MPU.
Before starting internal operation of the HD66727, control information is temporarily stored in these
registers to allow interfacing with various peripheral control devices or MPUs which operate at different
speeds. The internal operation of the HD66727 is determined by signals sent from the MPU. These signals,
which include register selection bit (RS), read/write bit (R/W), and the data bus (DB0 to DB7), make up the
HD66727 instructions. There are four categories of instructions that:
• Control display
• Control key scan
• Control power management
• Set internal RAM addresses
• Perform data transfer with internal RAM
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 HD66727 RAM addresses after each data
write can lighten the program load of the MPU.
While an instruction is being executed for internal operation, or during reset, no instruction other than the
busy flag/key scan 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. If an instruction is sent without checking the busy flag, the time
between the first instruction issue and next instruction issue must be longer than the instruction execution
time itself. Refer to Table 23 for the list of each instruction execution cycles (clock pulses). The execution
time depends on the operating clock frequency (oscillation frequency).
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