IDT70T633/1S

High-Speed 2.5V 512/256K x 18 Asynchronous Dual-Port Static RAM

Industrial and Commercial Temperature Ranges

20

Functional Description

TheIDT70T633/1providestwoportswithseparatecontrol,address

and I/O pins that permit independent access for reads or writes to any

location in memory. The IDT70T633/1 has an automatic power down

downcircuitrythatpermitstherespectiveporttogointoastandbymode

when not selected (CE = HIGH). When a port is enabled, access to the

entirememoryarrayispermitted.

Interrupts

If the user chooses the interrupt function, a memory location (mail

box or message center) is assigned to each port. The left port interrupt

Truth Table. The left port clears the interrupt through access of

port writes to memory location 7FFFF (HEX) and to clear the interrupt

message(18bits)at7FFFEor7FFFF(3FFFFor3FFFEforIDT70T631)

isuser-definedsinceitisanaddressableSRAMlocation.Iftheinterrupt

function is not used, address locations 7FFFE and 7FFFF are not used

asmailboxes,but aspartoftherandomaccessmemory.RefertoTruth

Table III for the interrupt operation.

Truth Table IV —

Address BUSY Arbitration

NOTES:

IDT70T633/1 are push-pull, not open drain outputs. On slaves the BUSY input internally inhibits writes.

2. "L" if the inputs to the opposite port were stable prior to the address and enable inputs of this port. "H" if the inputs to the opposite port became stable after the address

NOTES:

1. This table denotes a sequence of events for only one of the eight semaphores on the IDT70T633/1.

Inputs

Outputs

Function

X

X

NO MATCH

H

H

Normal

HX

MATCH

H

H

Normal

XH

MATCH

H

H

Normal

LL

MATCH

(2)

(2)

5670 tbl 18

Functions

Status

No Action

1

1

Semaphore free

Left Port Writes "0" to Semaphore

0

1

Left port has semaphore token

Right Port Writes "0" to Semaphore

0

1

No change. Right side has no write access to semaphore

Left Port Writes "1" to Semaphore

1

0

Right port obtains semaphore token

Left Port Writes "0" to Semaphore

1

0

No change. Left port has no write access to semaphore

Right Port Writes "1" to Semaphore

0

1

Left port obtains semaphore token

Left Port Writes "1" to Semaphore

1

1

Semaphore free

Right Port Writes "0" to Semaphore

1

0

Right port has semaphore token

Right Port Writes "1" to Semaphore

1

1

Semaphore free

Left Port Writes "0" to Semaphore

0

1

Left port has semaphore token

Left Port Writes "1" to Semaphore

1

1

Semaphore free

5670 tbl 19