SN74ACT7813

64

× 18 CLOCKED FIRST-IN, FIRST-OUT MEMORY

SCAS199B – JANUARY 1991 – REVISED APRIL 1998

8

POST OFFICE BOX 655303

offset values for AF/AE

The AF/AE flag has two programmable limits: the AE offset value (X) and the AF 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 = 8 are used. The AF/AE flag is high when the FIFO contains X or fewer

words or (64 – 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 and WRTCLK is low. On the following low-to-high transition of WRTCLK, the binary value on D0–D4 is

stored as the AE offset value (X) and the AF offset value (Y). Holding PEN low for another low-to-high transition

of WRTCLK reprograms Y to the binary value on D0–D4 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 the write enables (WRTEN1, WRTEN2). A maximum value of 31 can be programmed for either X or

Y (see Figure 4). To use the default values of X = Y = 8, PEN must be held high.

34

RESET

WRTCLK

PEN

WRTEN1

WRTEN2

D0–D4

IR

X and Y

Y

Figure 4. Programming X and Y Separately

–0.5 V to 7 V

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

–0.5 V to 7 V

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

Voltage range applied to a disabled 3-state output

–0.5 V to 5.5 V

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

Package thermal impedance,

74

°C/W

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

–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.

NOTE 1: The package thermal impedance is calculated in accordance with JESD 51.