SN74ACT3631

512

× 36

CLOCKED FIRST-IN, FIRST-OUT MEMORY

SCAS246G – AUGUST 1993 – REVISED APRIL 1998

16

POST OFFICE BOX 655303

(X + 1) Words in FIFO

tsu(EN)

CLKA

AE

ENB

ENA

th(EN)

tsu(EN)

tsk(2)†

tpd(C-AE)

X Words in FIFO

1

CLKB

2

tpd(C-AE)

th(EN)

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

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

NOTE A: FIFO write (CSA = L, W/RA = H, MBA = L), FIFO read (CSB = L, W/RB = H, MBB = L)

Figure 8. Timing for AE When FIFO Is Almost Empty

(512 – Y) Words in FIFO

tpd(C-AF)

tpd(C-AF)

tsu(EN)

CLKA

AF

ENB

ENA

tsu(EN)

th(EN)

[512 – (Y + 1)] Words in FIFO

th(EN)

tsk(2)‡

12

CLKB

‡ tsk(2) is the minimum time between a rising CLKA edge and a rising CLKB 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: FIFO write (CSA = L, W/RA = H, MBA = L), FIFO read (CSB = L, W/RB = H, MBB = L)

Figure 9. Timing for AF When the FIFO Is Almost Full