hd66765 Renesas Electronics Corporation., hd66765 Datasheet - Page 40

• Manufacturer Part Number: hd66765
• Description: 396-channel Segment Driver With Internal Ram For 4096-color Displays - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

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.
(Input/output)
DB15-0
(Input)
(Input)
CS*
E
Figure 31 Example of the Operation of High-Speed Consecutive Writing to RAM
Figure 30 Flow of Operation in High-Speed Consecutive Writing to RAM
Address
Note: When a high-speed RAM write is canceled, the next instruction must only be executed after
counter
(AC)
(R22h)
Index
the RAM write execution time has elapsed.
16
RAM address
(AC15 to 0)
RAM
data
1
1
RAM write data
RAM
data
(64 bits)
2
2
"0000"H "0001"H "0002"H "0003"H
RAM
data
Register 1
3
3
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.
RAM
data
4
4
RAM write
execution time
"0000"H
RAM data 1 to 4
RAM
data
1
5
RAM
data
2
6
Register 2
RAM
data
40
3
7
Microcomputer
RAM
data
GRAM
4
8
RAM write
execution time
RAM data 5 to 8
RAM
data
1
9
12
48
Register 3
"0004"H
RAM
data
10
2
RAM
data
3
11
RAM
data
12
4
Register 4
RAM write
execution time
RAM data 9 to 12
"0008"H
*
(R22h)
Index
"000A"H