6.06

16

IDT7005S/L

HIGH-SPEED 8K x 8 DUAL-PORT STATIC RAM

MILITARY AND COMMERCIAL TEMPERATURE RANGES

TRUTH TABLE II —

ADDRESS BUSY ARBITRATION

Inputs

Outputs

CE

CE

CE

CE

CE

CE

CE

CE

BUSY

BUSY

BUSY

(1)

BUSY

BUSY

BUSY

BUSY

(1)

Function

XX

NO MATCH

H

H

Normal

HX

MATCH

H

H

Normal

XH

MATCH

H

H

Normal

LL

MATCH

(2)

(2)

Write Inhibit

(3)

NOTES:

2738 tbl 18

1. Pins

IDT7005 are push-pull, not open drain outputs. On slaves the

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

simultaneously.

3. Writes to the left port are internally ignored when

internally ignored when

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

FUNCTIONAL DESCRIPTION

The IDT7005 provides two ports with separate control,

address and I/O pins that permit independent access for reads

or writes to any location in memory. The IDT7005 has an

automatic power down feature controlled by

CE. The CE

controls on-chip power down circuitry that permits the respec-

tive port to go into a standby mode when not selected (

CE

high). When a port is enabled, access to the entire memory

array is permitted.

INTERRUPTS

If the user chooses to use the interrupt function, a memory

location (mail box or message center) is assigned to each port.

The left port interrupt flag (

writes to memory location 1FFE (HEX), where a write is

defined as

clears the interrupt through access of address location 1FFE

when

Likewise, the right port interrupt flag (

the left port writes to memory location 1FFF (HEX) and to clear

the interrupt flag (

location 1FFF. The message (8 bits) at 1FFE or 1FFF is user-

defined, since it is an addressable SRAM location. If the

interrupt function is not used, address locations 1FFE and

1FFF are not used as mail boxes, but as part of the random

access memory. Refer to Truth Table for the interrupt opera-

tion.

BUSY LOGIC

Busy Logic provides a hardware indication that both ports

of the RAM have accessed the same location at the same

time. It also allows one of the two accesses to proceed and

signals the other side that the RAM is “Busy”. The busy pin can

then be used to stall the access until the operation on the other

side is completed. If a write operation has been attempted

from the side that receives a busy indication, the write signal

is gated internally to prevent the write from proceeding.

NOTES:

2738 tbl 19

1. This table denotes a sequence of events for only one of the eight semaphores on the IDT7005.