SN74ACT3631

512

× 36

CLOCKED FIRST-IN, FIRST-OUT MEMORY

SCAS246G – AUGUST 1993 – REVISED APRIL 1998

18

POST OFFICE BOX 655303

FIFO Filled to First Retransmit Word

CLKA

IR

tsu(EN)

th(EN)

RTM

tsk(1)†

CLKB

tpd(C-IR)

12

One or More Write Locations Available

† tsk(1) is the minimum time between a rising CLKB edge and a rising CLKA edge for IR to transition high in the next CLKA cycle. If the time

between the rising CLKB edge and rising CLKA edge is less than tsk(1), then IR can transition high one CLKA cycle later than shown.

Figure 12. IR Timing From the End of Retransmit Mode When One or More Write Locations Are Available

CLKA

AF

tsu(EN)

th(EN)

RTM

tsk(2)‡

(512 – Y) or More Words Past First Retransmit Word

CLKB

tpd(C-AE)

12

(Y + 1) or More Write Locations Available

‡ tsk(2) is the minimum time between a rising CLKB edge and a rising CLKA edge for AF to transition high in the next CLKA cycle. If the time

between the rising CLKB edge and rising CLKA edge is less than tsk(2), then AF can transition high one CLKA cycle later than shown.

NOTE A: Y is the value loaded in the AF flag offset register.

Figure 13. AF Timing From the End of Retransmit Mode When (Y + 1)

or More Write Locations Are Available