LH540245U-20 View Datasheet(PDF) - Sharp Electronics
Part Name
Description
MFG CO.
'LH540245U-20' PDF : 46 Pages View PDF
LH540235/45
TIMING DIAGRAMS (cont’d)
2048 x 18/4096 x 18 Synchronous FIFOs
Q [17:0]
DR1
tA
tA
RCLK
R1
REN1
R2
RT1
DR2
RT2
tA
A
RT3
DRT12
tA
DRT2
B
RT4
FL/RT
tENS
tRSF
PREVIOUS VALID FF
FF
PREVIOUS VALID PAF
PAF
PREVIOUS VALID HF
HF
PAE
PREVIOUS VALID PAE
tENH
tENS
UNKNOWN
UNKNOWN
UNKNOWN
PREVIOUS VALID EF
EF
NOTES:
1. It is not necessary for REN to be LOW for the device to recognize a retransmit request.
2. In order to actually read data words from the memory arrary, in IDT-Compatible
Operating Mode, REN = LOW; in Enhanced Operating Mode, also REN2 = HIGH
(and OE = LOW, if Control Register bit 05 = HIGH). In any case, LD = HIGH.
3. DRT1 is the data item in physical location zero of the FIFO memory array.
4. The asynchronous intermediate flags (corresponding to LOW Control-Register bits) will
show correct status three RCLK cycles after a retransmit operation, as is shown above.
(RT3, in the above RCLK waveform.)
5. The intermediate flags which have been synchronized to RCLK, by setting the appropriate
Control-Register bits to HIGH will show correct status after B , four RCLK cycles after a
retransmit operation. (RT4, in the above RCLK waveform.)
6. The intermediate flags which have been synchronized to WCLK, by setting the appropriate
Control-Register bits HIGH, will show correct status on the second WCLK rising edge after A ,
assuming that tSKEW1 was satisfied at A ; otherwise the flags will become valid on the third
WCLK rising edge after A .
7. Immediately after a reset operation, before any write operations have taken place, a retransmit
operation is a 'no-op', and does not change the state of any FIFO registers or flags.
8. In the special case that the FIFO memory array contains only one valid data item, the status
of HF and PAF should be ignored on a retransmit.
Figure 21. Retransmit Timing,
IDT-Compatible Operating Mode
34
tWFF
NEW VALID FF
tPAF
NEW VALID PAF
tHF
NEW VALID HF
NEW VALID PAE
tPAE
NEW VALID EF
tREF
540235-28
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