HD66765 Datasheet, PDF (40/71 Pages) Hitachi Semiconductor – 396-channel Segment Driver with Internal RAM for 4096-color Displays

HD66765
High-Speed Burst RAM Write Function
The HD66765 has a high-speed burst RAM-write function that can be used to write data to RAM in one-
fourth the access time required for an equivalent standard RAM-write operation. This function is
especially suitable for applications which require the high-speed rewriting of the display data, for
example, display of color animations, etc.
When the high-speed RAM-write mode (HWM) is selected, data for writing to RAM is once stored to the
HD66765 internal register. When data is selected four times per word, all data is written to the on-chip
RAM. While this is taking place, the next data can be written to an internal register so that high-speed
and consecutive RAM writing can be executed for animated displays, etc.
tion ^{Microcomputer}
a ₁₂
cific ^Address
counter
e _(AC)
ary ^{Sp 16}
Register 1
Register 2
Register 3
48
Register 4
"0000"H "0001"H "0002"H "0003"H
GRAM
limin ^{Figure 30 Flow of Operation in High-Speed Consecutive Writing to RAM}
Pre ^CS*
(Input)
123 4123 4 123 4
E
(Input)
DB15-0
(Input/output)
Index
(R22h)
RAM RAM RAM RAM RAM RAM RAM RAM RAM RAM RAM RAM
data data data data data data data data data data data data
1 2 3 4 5 6 7 8 9 10 11 12
Index
(R22h)
RAM write
execution time
RAM write
execution time
RAM write
execution time ^*
RAM write data
(64 bits)
RAM data 1 to 4
RAM data 5 to 8
RAM data 9 to 12
RAM address
(AC15 to 0)
"0000"H
"0004"H
"0008"H
"000A"H
♦ The lower two bits of the address must be set in the following way in high-speed write mode.
When ID0 becomes 0, the lower two bits of the address must be set to 11
When ID1 becomes 1, the lower two bits of the address must be set to 00.
Note: When a high-speed RAM write is canceled, the next instruction must only be executed after
the RAM write execution time has elapsed.
Figure 31 Example of the Operation of High-Speed Consecutive Writing to RAM
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