COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72805LB/72815LB/72825LB/72845LB CMOS Dual SyncFIFO
TM
256 x 18, 512 x 18, 1,024 x 18, and 4,096 x 18
16
Figure 15. Half-Full Flag Timing (IDT Standard and FWFT Modes)
Figure 14. Asynchronous Programmable Almost-Full Flag Timing (IDT Standard and FWFT Modes)
NOTES:
1. m = PAF offset.
2. D = maximum FIFO Depth.
In IDT Standard Mode: D = 256 for the IDT72805, 512 for the IDT72815, 1,024 for the IDT72825 and 4,096 for the IDT72845.
In FWFT Mode:
D = 257 for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825 and 4,097 for the IDT72845.
3. PAF is asserted to LOW on WCLK transition and reset to HIGH on RCLK transition.
4. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (0,1,1) or (1,1,1) during Reset.
NOTES:
1. D = maximum FIFO Depth.
In IDT Standard Mode: D = 256 for the IDT72805, 512 for the IDT72815, 1,024 for the IDT72825 and 4,096 for the IDT72845.
In FWFT Mode:
D = 257 for the IDT72805, 513 for the IDT72815, 1,025 for the IDT72825 and 4,097 for the IDT72845.
2. For IDT Standard Mode.
3. For FWFT Mode.
4. Select this mode by setting (FL, RXI, WXI) = (0,0,0), (0,0,1), (0,1,0), (1,0,0), (1,0,1) or (1,1,0) during Reset.
WCLK
t
CLKH
t
CLKL
t
ENS
t
ENH
WEN
PAF
t
ENS
t
PAFA
D - (m + 1) words in FIFO
RCLK
t
PAFA
REN
(1)
3139 drw 14
D - m words in FIFO
D - (m + 1) words in FIFO
WCLK
t
ENS
t
ENH
WEN
HF
t
ENS
t
HF
RCLK
t
HF
REN
3139 drw 15
t
CLKL
t
CLKH
D/2 words in FIFO
(2)
,
[
+ 1
]
words in FIFO
(3)
D/2 + 1 words in FIFO
(2)
,
[
+ 2
]
words in FIFO
(3)
D-1
2
D/2 words in FIFO
(2)
,
[
+ 1
]
words in FIFO
(3)
D-1
2
D-1
2
