HD66420 Datasheet, PDF (10/52 Pages) Hitachi Semiconductor – (RAM-Provided 160 Channel 4-Level Grey Scale Driver for Dot Matrix Graphics LCD)

HD66420
MPU Interface
The HD66420 can interface directly to an MPU through an 8-bit data bus or through an I/O port (figure 2).
The MPU can access the HD66420 internal registers independently of internal clock timing.
The index register can be directly accessed but the other registers (data registers) cannot. Before accessing
a data register, its register number must be written to the index register. Once written, the register number is
held until it is rewritten, enabling the same register to be consecutively accessed without having to rewrite
to the register number for each access. An example of a register access sequence is shown in figure 3.
A15 - A0
Z80
A0
RD
WR
D0 - D7
decoder
8
CS
RS
RD _HD66420
WR
DB0 - DB7
a) Interface through Bus
C0
C1
C2
H8/325 C3
A0 - A7
8
CS
RS
RD
WR
HD66420
DB0 - DB7
b) Interface through I/O Port
Figure 2 8-Bit MPU Interface Examples
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