SN74ALVC7803

512

× 18

CLOCKED FIRST-IN, FIRST-OUT MEMORY

SDAS274 – JANUARY 1995

8

POST OFFICE BOX 655303

offset values for AF/AE

The AF/AE flag has two programmable limits: the almost-empty offset value (X) and the almost-full offset value

(Y). They can be programmed after the FIFO is reset and before the first word is written to memory. If the offsets

are not programmed, the default values of X = Y = 64 are used. The AF/AE flag is high when the FIFO contains

X or less words or (512 minus Y) or more words.

Program enable (PEN) should be held high throughout the reset cycle. PEN can be brought low only when IR

is high. On the following low-to-high transition of WRTCLK, the binary value on D0 – D7 is stored as the almost

empty offset value (X) and the almost full offset value (Y). Holding PEN low for another low-to-high transition

of WRTCLK reprograms Y to the binary value on D0 – D7 at the time of the second WRTCLK low-to-high

transition. When the offsets are being programmed, writes to the FIFO memory are disabled regardless of the

state of WRTEN1 and WRTEN2. A maximum value of 255 can be programmed for either X or Y

(see Figure 4). To use the default values of X = Y = 64, PEN must be held high.

34

RESET

WRTCLK

PEN

WRTEN1

WRTEN2

D0 – D7

IR

X and Y

Y

Figure 4. Programming X and Y Separately

– 0.5 V to 4.6 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

–0.5 V to 4.6 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

*50 mA

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

"50 mA

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

"50 mA

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

"100 mA

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Voltage applied to a disabled 3-state output

3.6 V

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

0

°C to 70°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Storage temperature range

– 65

°C to 150°C

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

† Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device. These are stress ratings only, and

functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not

implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.

NOTES:

1. The input and output voltage ratings can be exceeded if the input and output clamp current ratings are observed.

2. This value is limited to 4.6 V maximum.