12
IDT72801/728211/72821/72831/72841/72851 DUAL CMOS SyncFIFO
TM
DUAL 256 x 9, DUAL 512 x 9, DUAL 1K x 9, DUAL 2K x 9, DUAL 4K x 9, DUAL 8K x 9
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
MARCH 2013
Figure 10. Programmable Full Flag Timing
NOTES:
1. m = PAF offset.
2. (256-m) words for the IDT72801; (512-m) words the IDT72811; (1,024-m) words for the IDT72821; (2,048-m) words for the IDT72831; (4,096-m) words for the IDT72841; or (8,192-m)
words for the IDT72851.
3. tSKEW2 is the minimum time between a rising RCLKA (RCLKB) edge and a rising WCLKA (WCLKB) edge for PAFA (PAFB) to change during that clock cycle. If the time between the
rising edge of RCLKA (RCLKB) and the rising edge of WCLKA (WCLKB) is less than tSKEW2, then PAFA (PAFB) may not change state until the next WCLKA (WCLKB) rising edge.
4. If a write is performed on this rising edge of the write clock, there will be Full - (m-1) words in FIFO A (B) when PAFA (PAFB) goes LOW.
tENS
tENH
tENS
tENH
tENS tENH
WCLKA
(WCLKB)
WENA1
(WENB1)
WENA2 (WENB2)
(If Applicable)
PAFA
(PAFB)
RCLKA (RCLKB)
RENA1, RENA2
(RENB1, RENB2)
(4)
(1)
tPAF
Full - (m+1) words in FIFO
Full - m words in FIFO
(2)
tCLKH
tCLKL
tSKEW2
(3)
tPAF
3034 drw 11
WCLKA (WCLKB)
WENA1
(WENB1)
WENA2 (WENB2)
(If Applicable)
PAEA,
PAEB
RCLKA (RCLKB)
RENA1, RENA2
(RENB1, RENB2)
t
ENS
t
ENH
t
ENS
t
ENH
t
SKEW2
(2)
t
ENS
t
ENH
t
PAE
t
PAE
(3)
(1)
n words in FIFO
n+1 words in FIFO
t
CLKH
t
CLKL
3034 drw 12
NOTES:
1. n = PAE offset.
2. tSKEW2 is the minimum time between a rising WCLKA (WCLKB) edge and a rising RCLKA (RCLKB) edge for PAEA (PAEB) to change during that clock cycle. If the time between the
rising edge of WCLKA (WCLKB) and the rising edge of RCLKA (RCLKB) is less than tSKEW2, then PAEA (PAEB) may not change state until the next RCLKA (RCLKB) rising edge.
3. If a read is performed on this rising edge of the read clock, there will be Empty + (n-1) words in FIFO A (B) when PAEA (PAEB) goes LOW.
Figure 11. Programmable Empty Flag Timing
