4

IDT723631/723641/723651 CMOS SyncFIFO

™

512 x 36, 1024 x 36, 2048 x 36

COMMERCIAL TEMPERATURE RANGE

PIN DESCRIPTION

Symbol

Name

I/O

Description

A0-A35

Port-A Data

I/O 36-bit bidirectional data port for side A.

AE

Almost-Empty Flag

O

Programmable flag synchronized to CLKB. It is LOW when the number of

words in the FIFO is less than or equal to the value in the almost-empty

register (X).

AF

Almost-Full Flag.

O

Programmable flag synchronized to CLKA. It is LOW when the number of

empty locations in the FIFO is less than or equal to the value in the almost-full

offset register (Y).

B0-B35

Port-B Data.

I/O 36-bit bidirectional data port for side B.

CLKA

Port-A Clock

I

CLKA is a continuous clock that synchronizes all data transfers through port-A

and may be aynchronous or coincident to CLKB. IR and

AF are synchronous

to the LOW-to-HIGH transition of CLKA.

CLKB

Port-B Clock

I

CLKB is a continuous clock that synchronizes all data transfers through port-B

and may be asynchronous or coincident to CLKA. OR and

AE are synchro

nous to the LOW-to-HIGH transition of CLKB.

CSA

Port-A Chip Select

I

CSA must be LOW to enable a LOW-to-HIGH transition of CLKA to read or

write data on port-A. The A0-A35 outputs are in the high-impedance state

when

CSA is HIGH.

CSB

Port-B Chip Select

I

CSB must be LOW to enable a LOW-to-HIGH transition of CLKB to read or

write data on port-B. The B0-B35 outputs are in the high-impedance state

when

CSB is HIGH.

ENA

Port-A Enable

I

ENA must be HIGH to enable a LOW-to-HIGH transition of CLKA to read or

write data on port-A.

ENB

Port-B Enable

I

ENB must be HIGH to enable a LOW-to-HIGH transition of CLKB to read or

write data on port-B.

FS1/

SEN, Flag-Offset Select 1/

I

FS1/

SEN and FS0/SD are dual-purpose inputs used for flag offset register

FS0/SD

Serial Enable,

programming. During a device reset, FS1/

SEN and FS0/SD selects the flag

Flag Offset 0/

offset programming method. Three offset register programming methods are

Serial Data

available: automatically load one of two preset values, parallel load from port

A, and serial load. When serial load is selected for flag offset register program-

ming, FS1/

SEN is used as an enable synchronous to the LOW-to-HIGH

transition of CLKA. When FS1/

SEN is LOW, a rising edge on CLKA load the

bit present on FS0/SD into the X and Y registers. The number of bit writes

required to program the offset registers is 18/20/22. The first bit write stores

the Y-register MSB and the last bit write stores the X-register LSB.

IR

Input-Ready Flag

O

IR is synchronized to the LOW-to-HIGH transition of CLKA. When IR is LOW,

the FIFO is full and writes to its array are disabled. When the FIFO is in

retransmit mode, IR indicates when the memory has been filled to the point of

the retransmit data and prevents further writes. IR is set LOW during reset

and is set HIGH after reset.

MBA

Port-A Mailbox Select

I

A HIGH level chooses a mailbox register for a port-A read or write operation.

MBB

Port-B Mailbox Select

I

A HIGH level chooses a mailbox register for a port-B read or write operation.

When the B0-B35 outputs are active, a HIGH level on MBB selects data from

the mail1 register for output and a LOW level selects FIFO data for output.

MBF1

Mail1 Register Flag

O

MBF1 is set LOW by the LOW-to-HIGH transition of CLKA that writes data to

the mail1 register.

MBF1 is set HIGH by a LOW-to-HIGH transition of CLKB

when a port-B read is selected and MBB is HIGH.

MBF1 is set HIGH by a

reset.

3023 tbl 01