4

COMMERCIALTEMPERATURERANGE

IDT723663/723673 CMOS SyncFIFOTM WITH BUS-MATCHING

4,096 x 36 x 2 and 8,192 x 36 x 2

PIN DESCRIPTIONS

Symbol

Name

I/O

Description

A0-A35

Port A Data

I/O

36-bitbidirectionaldataportforsideA.

AE

Almost-EmptyFlag

O

Programmable Almost-Empty flag synchronized to CLKB. It is LOW when the number of words in the

(Port B)

FIFO is less than or equal to the value in the Almost-Empty B offset register, X.

AF

Almost-FullFlag

O

ProgrammableAlmost-FullflagsynchronizedtoCLKA.ItisLOWwhenthenumberofempty

(Port A)

locations in the FIFO is less than or equal to the value in the Almost-Full A offset register, Y.

B0-B35

Port B Data

I/O

36-bitbidirectionaldataportforsideB.

BE/FWFT

Big-Endian/

I

This is a dual purpose pin. During Master Reset, a HIGH on BE will select Big-Endian operation. In

FirstWord

this case, depending on the bus size, the most significant byte or word written to Port A is read from

Fall Through

PortBfirst.ALOWonBEwillselectLittle-Endianoperation.Inthiscase,theleastsignificantbyteor

word written to Port A is read from Port B first. After Master Reset, this pin selects the timing mode. A

HIGH on FWFT selects IDT Standard mode, a LOW selects First Word Fall Through mode. Once

the timing mode has been selected, the level on FWFT must be static throughout device operation.

BM(1)

Bus-MatchSelect

I

A HIGH on this pin enables either byte or word bus width on Port B, depending on the state of

(Port B)

SIZE. A LOW selects long word operation. BM works with SIZE and BE to select the bus size and

endian arrangement for Port B.The level of BM must be static throughout device operation.

CLKA

Port A Clock

I

CLKA is a continuous clock that synchronizes all data transfers through Port A and can be

asynchronous or coincident to CLKB. FF/IR and AF are synchronized to the LOW-to-HIGH

transitionofCLKA.

CLKB

Port B Clock

I

CLKB is a continuous clock that synchronizes all data transfers through Port B and can be

asynchronous or coincident to CLKA. EF/OR and AE are synchronized to the LOW-to-HIGH

transitionofCLKB.

CSA

Port A Chip

I

CSA must be LOW to enable to LOW-to-HIGH transition of CLKA to read or write on Port A.The

Select

A0-A35 outputs are in the high-impedance state when CSA is HIGH.

CSB

Port B Chip

I

CSB must be LOW to enable a LOW-to-HIGH transition of CLKB to read or write data on Port B.

Select

The B0-B35 outputs are in the high-impedance state when CSB is HIGH.

EF/OR

Empty/Output

O

This is a dual function pin. In the IDT Standard mode, the EF function is selected. EFindicates

Ready Flag

whetherornottheFIFOmemoryisempty.IntheFWFTmode,theORfunctionisselected.ORindicates

(Port B)

thepresenceofvaliddataontheB0-B35outputs,availableforreading. EF/ORissynchronizedtothe

LOW-to-HIGHtransitionofCLKB.

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.

FF/IR

Full/Input

O

This is a dual function pin. In the IDT Standard mode, the FF function is selected. FF indicates

Ready Flag

whether or not the FIFO memory is full. In the FWFT mode, the IR function is selected. IR indicates

(Port A)

whether or not there is space available for writing to the FIFO memory. FF/IR is synchronized to the

LOW-to-HIGHtransitionofCLKA.

FS0/SD

FlagOffsetSelect0/

I

FS1/SEN and FS0/SD are dual-purpose inputs used for flag offset register programming. During

SerialData,

Reset,FS1/SENandFS0/SD,togetherwithFS2selecttheflagoffsetprogrammingmethod. Three

offsetregisterprogrammingmethodsareavailable:automaticallyloadoneoffivepresetvalues(8,

16, 64, 256 or 1,024), parallel load from Port A, and serial load.

FS1/SEN

FlagOffsetSelect1/

I

SerialEnable

When serial load is selected for flag offset register programming, 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

FS2(1)

FlagOffsetSelect2

I

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 24 for the IDT723663, and 26 for the IDT723673. The first bit write

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

MBA

Port A Mailbox

I

A HIGH level on MBA chooses a mailbox register for a Port A read or write operation.

Select

MBB

Port B Mailbox

I

A HIGH level on MBB chooses a mailbox register for a Port B read or write operation. When the

Select

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.