HD66781 Datasheet, PDF (153/196 Pages) Renesas Technology Corp – 720-channel Source Driver for a-Si TFT/Low Temperature Poly-Si TFT Panels with 262,144-color display RAM

HD66781
Preliminary
High-Speed Burst RAM Write Function
The HD66781 incorporates high-speed burst RAM-write function, which writes data to RAM about half the
time required for the normal RAM write. This function is especially useful for applications, which require
high-speed display data rewrite, such as colored moving picture display and so on.
In the high-speed RAM-write mode (HWM=1), data to write to RAM is temporarily stored to the internal
register of HD66781 and then written to RAM by horizontal line in the area specified by the window
address. Since the data stored in the register are written to RAM at once, it is possible to write next data to
the internal register while data are being written from the internal register to RAM. This reduces the
frequency of RAM access to minimum and enables consecutive high-speed access to the internal RAM
with low power consumption, which is required for moving picture display.
Microcomputer
Latch circuit
18
Address
counter
AC
17
Register 1 Register 2
Register n
18’h0-0000
18’h0-0001
18 x n
18’h0-0003
GRAM
High-speed consecutive access to RAM, operational flow
CS
input
WR
input
DB17-0
input
index
(R202)
1 2 ... n 1 2 ... n 1 2 ... n
RAM data
(1) (2) ... (n) (1) (2) ... (n) (1) (2) ... (n)
index
(R202)
RAM write
execution time
RAM write
execution time
RAM write execution time x 2
Note)
RAM write data
(18 x n bits)
RAM address
(AC17-0)
RAM
data
(1) - (n)
18’h00000 –
18’h0000n
RAM
data
(n+1) - (2n)
18’h00100 –
18’h0010n
RAM
data
(2n+1) - (3n)
18’h00200 –
18’h0020n
High-speed consecutive access to RAM (HWM = “1”)
Note 1) When making a transition from the high-speed RAM write to the index write, wait at least 2 bus cycle
time (tcycw) in the normal write mode after RAM write before executing next instructions.
Rev.0.5, July.31.2003, page 153 of 196