SN74ACT3651

2048

× 36

CLOCKED FIRST-IN, FIRST-OUT MEMORY

SCAS439D – JUNE 1994 – REVISED FEBRUARY 1999

1

POST OFFICE BOX 655303

Asynchronous or Coincident

to Port B

Almost-Empty Flags

CLKA

by CLKB

Technology

and SN74ACT3641

Quad Flat (PCB) and 132-Pin Plastic Quad

Flat (PQ) Packages

description

The SN74ACT3651 is a high-speed, low-power, CMOS clocked FIFO memory that supports clock frequencies

up to 67 MHz and has read access times as fast as 11 ns. The 2048

× 36 dual-port SRAM FIFO buffers data

from port A to port B. The FIFO memory has retransmit capability, which allows previously read data to be

accessed again. The FIFO has flags to indicate empty and full conditions and two programmable flags (almost

full and almost empty) to indicate when a selected number of words is stored in memory. Communication

between each port takes place with two 36-bit mailbox registers. Each mailbox register has a flag that signals

when new mail has been stored. Two or more devices are used in parallel to create wider data paths. Expansion

is also possible in word depth.

The SN74ACT3651 is a clocked FIFO, which means each port employs a synchronous interface. All data

transfers through a port are gated to the low-to-high transition of a continuous (free-running) port clock by enable

signals. The continuous clocks for each port are independent of one another and can be asynchronous or

coincident. The enables for each port are arranged to provide a simple interface between microprocessors

and/or buses with synchronous control.

The input-ready (IR) flag and almost-full (AF) flag of the FIFO are two-stage synchronized to CLKA. The

output-ready (OR) flag and almost-empty (AE) flag of the FIFO are two-stage synchronized to CLKB. Offset

values for AF and AE are programmed from port A or through a serial input.

The SN74ACT3651 is characterized for operation from 0

°C to 70°C.

For more information on this device family, see the following application reports:

(literature number SCAA009)

(literature number SCAA007)

Copyright

© 1999, 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.

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.