COMMERCIALANDINDUSTRIAL
TEMPERATURERANGES
IDT72805LB/72815LB/72825LB/72835LB/72845LB CMOS Dual SyncFIFOTM
256 x 18, 512 x 18, 1,024 x 18, 2,048 x 18 and 4,096 x 18
22
JANUARY 13, 2009
Figure 27.
OR
OR Flag Timing and First Word Fall Through when FIFO is Empty (FWFT mode)
NOTES:
1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge to guarantee that
EF will go HIGH after one RCLK cycle plus tREF. If the time between the rising edge
of WCLK and the rising edge of RCLK is less than tSKEW1. then the
EF deassertion may be delayed an extra RCLK cycle.
2.
LD = HIGH
3. Select this mode by setting (
FL, RXI, WXI) = (0,1,0) or (1,1,0) during Reset.
Figure 26. Read Cycle Timing with Double Register-Buffered
EF
EF (IDT Standard Timing)
NOTES:
1. tSKEW1 is the minimum time between a rising WCLK edge and a rising RCLK edge for
OR to go HIGH during the current cycle. If the time between the rising edge of WLCK and the rising
edge of RCLK is less than tSKEW1, then the
OR deassertion may be delayed one extra RCLK cycle.
2.
LD = HIGH, OE = LOW
3. Select this mode by setting (
FL, RXI, WXI) = (0,0,1) or (1,0,1) during Reset.
NO OPERATION
RCLK
REN
EF
tCLKL
tENH
tREF
LAST WORD
tA
tOLZ
tOE
Q0 - Q17
OE
WCLK
WEN
3139 drw 26
D0 - D17
tENS
tENH
tDS
tDH
FIRST WORD
tOHZ
tCLK
12
tREF
tSKEW1
tCLKH
(1)
W1
W2
W4
W[n +2]
W[n+3]
WCLK
WEN
D0
- D17
RCLK
tDH
tDS
tENS
tSKEW1
REN
Q0
- Q17
tDS
tA
tREF
OR
W1
DATA IN OUTPUT REGISTER
(1)
W3
1
2
3
tENH
tREF
3139 drw 27