SN74ALVC3631_07 Datasheet, PDF (7/29 Pages) Texas Instruments – SYNCHRONOUS FIRST-IN, FIRST-OUT MEMORIES

SN74ALVC3631, SN74ALVC3641, SN74ALVC3651
512 × 36, 1024 × 36, 2048 × 36
SYNCHRONOUS FIRST-IN, FIRST-OUT MEMORIES
SDMS025B – OCTOBER 1999 – REVISED JUNE 2000
serial load
To program the X and Y registers serially, the device is reset with FS0/SD and FS1/SEN high during the
low-to-high transition of RST. After this reset is complete, the X-and Y-register values are loaded bitwise through
FS0/SD on each low-to-high transition of CLKA that FS1/SEN is low. Eighteen (SN74ALVC3631), twenty
(SN74ALVC3641), and twenty-two (SN74ALVC3651) bit writes are needed to complete the programming. The
first bit write stores the most-significant bit of the Y register and the last bit write stores the least-significant bit
of the X register. Each register value can be programmed from 1 to 508 (SN74ALVC3631), 1 to 1020
(SN74ALVC3641), and 1 to 2044 (SN74ALVC3651).
When the option is chosen to program the offset registers serially, the IR flag remains low until all register bits
are written. The IR flag is set high by the low-to-high transition of CLKA after the last bit is loaded, to allow normal
FIFO operation.
FIFO write/read operation
The state of the port-A data (A0–A35) outputs is controlled by the port-A chip select (CSA) and the port-A
write/read select (W/RA). The A0–A35 outputs are in the high-impedance state when either CSA or W/RA is
high. The A0–A35 outputs are active when both CSA and W/RA are low.
Data is loaded into the FIFO from the A0–A35 inputs on a low-to-high transition of CLKA when CSA and the
port-A mailbox select (MBA) are low, W/RA, the port-A enable (ENA), and the IR flag are high (see Table 2).
Writes to the FIFO are independent of any concurrent FIFO reads.
Table 2. Port-A Enable Function Table
CSA
H
L
L
L
L
L
L
L
W/RA
X
H
H
H
L
L
L
L
ENA
X
L
H
H
L
H
L
H
MBA
X
X
L
H
L
L
H
H
CLKA
X
X
↑
↑
X
↑
X
↑
A0–A35 OUTPUTS
In high-impedance state
In high-impedance state
In high-impedance state
In high-impedance state
Active, mail2 register
Active, mail2 register
Active, mail2 register
Active, mail2 register
PORT FUNCTION
None
None
FIFO write
Mail1 write
None
None
None
Mail2 read (set MBF2 high)
The port-B control signals are identical to those of port A, with the exception that the port-B write/read select
(W/RB) is the inverse of the W/RA. The state of the port-B data (B0–B35) outputs is controlled by the port-B
chip select (CSB) and W/RB. The B0–B35 outputs are in the high-impedance state when either CSB is high or
W/RB is low. The B0–B35 outputs are active when CSB is low and W/RB is high.
Data is read from the FIFO to its output register on a low-to-high transition of CLKB when CSB and MBB are
low, W/RB, ENB, and the OR flag are high (see Table 3). Reads from the FIFO are independent of any concurrent
FIFO writes.
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