IDT7208 CMOS ASYNCHRONOUS FIFO

65,536 x 9

COMMERCIAL TEMPERATURE RANGES

5.06

5

Outputs:

FULL FLAG (

FF

FF) — The Full Flag (FF) will go LOW, inhibiting

further write operations, when the device is full. If the read

pointer is not moved after Reset (

RS), the Full Flag (FF) will go

LOW after 65,536 writes.

EMPTY FLAG (

EF

EF) — The Empty Flag (EF) will go LOW,

inhibiting further read operations, when the read pointer is equal

to the write pointer, indicating that the device is empty.

EXPANSION OUT/HALF-FULL FLAG (

XO

XO/HF

HF) — This is a

dual-purpose output. In the single device mode, when Expan-

sion In (

XI)is grounded, this output acts as an indication of a half-

full memory.

After half of the memory is filled, and at the falling edge of the

next write operation, the Half-Full Flag (

HF) will be set to LOW

Figure 2. Reset

Figure 3. Asynchronous Write and Read Operation

NOTE:

1.

and will remain set until the difference between the write pointer

and read pointer is less than or equal to one half of the total

memory of the device. The Half-Full Flag (

HF) is then reset by

the rising edge of the read operation.

In the Depth Expansion Mode, Expansion In (

XI) is con-

nected to Expansion Out (

XO) of the previous device. This

output acts as a signal to the next device in the Daisy Chain by

providing a pulse to the next device when the previous device

reaches the last location of memory. There will be an

XO pulse

when the Write pointer reaches the last location of memory, and

an additional

XO pulse when the Read pointer reaches the last

location of memory.

bit wide data. These outputs are in a high-impedance condition

whenever Read (

R) is in a HIGH state.

W

RS

R

EF

HF, FF

3274 drw 05

R

W

D

DATA

0

VALID

IN

VALID

VALID

3274 drw 06