hd66420 Renesas Electronics Corporation., hd66420 Datasheet - Page 10

• Manufacturer Part Number: hd66420
• Description: Ram-provided 160 Channel 4-level Grey Scale Driver For Dot Matrix Graphics Lcd
• Manufacturer: Renesas Electronics Corporation.

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.
10
H8/325
Z80
A15 - A0
Figure 2 8-Bit MPU Interface Examples
D0 - D7
A0 - A7
a) Interface through Bus
b) Interface through I/O Port
WR
RD
A0
C0
C1
C2
C3
decoder
8
8
CS
RS
RD
WR
DB0 - DB7
CS
RS
RD
WR
DB0 - DB7
HD66420
HD66420