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AL422
AL422B
January 23, 2001
13
8.0 Functional Description
The AL422 is a video frame buffer consisting of DRAM that works like a FIFO which is long enough
to hold up to 819x480 bytes of picture information and fast enough to operate at 50MHz. The
functional block diagram is as follows:
The I/O pinouts and functions are described as follows:
DI7~DI0 Data Input: Data is input on the rising edge of the cycle of WCK when /WE is pulled low
(enabled).
DO7~DO0 Data Output: Data output is synchronized with the RCK clock. Data is obtained at the
rising edge of the RCK clock when /RE is pulled low. The access time is defined from the rising edge
of the RCK cycle.
WCK Write Clock Input: The write data input is synchronized with this clock. Write data is input at
the rising edge of the WCK cycle when /WE is pulled low (enabled). The internal write address
pointer is incremented automatically with this clock input.
RCK Read Clock Input: The read data output is synchronized with this clock. Read data output at
the rising edge of the RCK cycle when /OE is pulled low (enabled). The internal read address pointer
is incremented with this clock input.
/WE Write Enable Input: /WE controls the enabling/disabling of the data input. When /WE is
pulled low, input data is acquired at the rising edge of the WCK cycle. When /WE is pulled high, the
384k x8
Memory Cell Array
SRAM
Cache
Timing Generator
& Arbiter
Write
Address
Counter
Read
Address
Counter
Refresh Address
Counter
DI7~
DI0
DO7~
DO0
/OE
RCK
/RRST
/RE
WCK
/WRST
/WE
AL422-03 Block Diagram
Input
Buffer
Write
Data
Register
Read
Data
Register
Output
Buffer
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