SN74ALS2238 Datasheet, PDF (1/11 Pages) Texas Instruments – 32 X 9 X 2 ASYNCHRONOUS BIDIRECTIONAL FIRST-IN, FIRST-OUT MEMORY

SN74ALS2238
32 × 9 × 2 ASYNCHRONOUS BIDIRECTIONAL FIRSTĆIN, FIRSTĆOUT MEMORY
SDAS182 − APRIL 1990
D Independent Asychronous Inputs and
Outputs
D Bidirectional
D 32 Words by 9 Bits
D Programmable Depth
D Data Rates from 0 to 40 MHz
D Fall-Through Time . . . 22 ns Typ
D 3-State Outputs
description
This 576-bit memory uses advanced low-power
Schottky IMPACT-X technology and features
high speed and fast fall-through times. It consists
of two FIFOs organized as 32 words by 9 bits
each.
A FIFO memory is a storage device that allows
data to be written into and read from its array at
independent data rates. These FIFOs are
designed to process data at rates from 0 to 40
MHz in a bit-parallel format, word by word.
The SN74ALS2238 consists of bus-transceiver
circuits, two 32 × 9 FIFOs, and control circuitry
arranged for multiplexed transmission of data
directly from the data bus or from the internal FIFO
memories. Enables GAB and GBA are provided to
control the transceiver functions. The SAB and
SBA control pins are provided to select whether
real-time or stored data is transferred. The
circuitry used for select control eliminates the
typical decoding glitch that occurs in a multiplexer
during the transition between stored and real-time
data. A low level selects real-time data and a high
selects stored data. Eight fundamental
bus-management functions can be performed as
shown in Figure 1.
Data on the A or B data bus, or both, is written into
the FIFOs on a low-to-high transition at the load
clock (LDCKA or LDCKB) input and is read out on
a low-to-high transition at the unload clock
(UNCKA or UNCKB) input. The memory is full
when the number of words clocked in exceeds, by
the defined depth, the number of words clocked
out.
N PACKAGE
(TOP VIEW)
RSTA 1
DAF 2
A0 3
A1 4
A2 5
GND 6
A3 7
A4 8
A5 9
A6 10
GND 11
V_CC 12
A7 13
A8 14
LDCKA 15
FULLA 16
UNCKB 17
EMPTYB 18
SAB 19
GAB 20
40 RSTB
39 DBF
38 B0
37 B1
36 B2
35 GND
34 B3
33 B4
32 B5
31 B6
30 GND
29 V_CC
28 B7
27 B8
26 LDCKB
25 FULLB
24 UNCKA
23 EMPTYA
22 SBA
21 GBA
FN PACKAGE
(TOP VIEW)
GND
V_CC
A3
A4
A5
A6
GND
V_CC
A7
A8
LDCKA
6 5 4 3 2 1 44 43 42 41 40
7
39
8
38
9
37
10
36
11
35
12
34
13
33
14
32
15
31
16
30
17
29
18 19 20 21 22 23 24 25 26 27 28
B2
GND
V_CC
B3
B4
B5
B6
GND
V_CC
B7
B8
When the memory is full, LDCK signals have no effect on the data residing in memory. When the memory is
empty, UNCK signals have no effect.
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
IMPACT-X is a trademark of Texas Instruments Incorporated.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of Texas Instruments
standard warranty. Production processing does not necessarily include
testing of all parameters.
Copyright  1990, Texas Instruments Incorporated
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
• POST OFFICE BOX 1443 HOUSTON, TEXAS 77251−1443
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