12
COMMERCIALTEMPERATURERANGE
IDT72V3653/72V3663/72V3673 3.3V CMOS SyncFIFOTM WITH
BUS-MATCHING 2,048 x 36, 4,096 x 36, and 8,192 x 36
LOW, and
EF/OR is HIGH (see Table 3). FIFO reads on Port B are
independent of any concurrent writes on Port A.
The setup and hold time constraints to the port clocks for the port Chip
SelectsandWrite/Readselectsareonlyforenablingwriteandreadoperations
andarenotrelatedtohigh-impedancecontrolofthedataoutputs. Ifaportenable
is LOW during a clock cycle, the port’s Chip Select and Write/Read select may
change states during the setup and hold time window of the cycle.
When operating the FIFO in FWFT mode and the Output Ready flag is
LOW, the next word written is automatically sent to the FIFO’s output register
bytheLOW-to-HIGHtransitionoftheportclockthatsetstheOutputReadyflag
HIGH. WhentheOutputReadyflagisHIGH,dataresidingintheFIFO’smemory
array is clocked to the output register only when a read is selected using the
port’s Chip Select, Write/Read select, Enable, and Mailbox select.
When operating the FIFO in IDT Standard mode, regardless of whether
the Empty Flag is LOW or HIGH, data residing in the FIFO’s memory array is
clocked to the output register only when a read is selected using the port’s
Chip Select, Write/Read select, Enable, and Mailbox select. Port A Write
timing diagram can be found in Figure 7. Relevant Port B Read timing
diagrams together with Bus-Matching and Endian select can be found in
Figure 8, 9 and 10.
SYNCHRONIZED FIFO FLAGS
Each FIFO is synchronized to its port clock through at least two flip-flop
stages. Thisisdonetoimproveflag-signalreliabilitybyreducingtheprobability
of metastable events when CLKA and CLKB operate asynchronously to one
another.
FF/IR, and AF are synchronized to CLKA. EF/OR and AE are
CSB
W/RB
ENB
MBB
CLKB
Data B (B0-B35) I/O
Port Functions
H
X
High-Impedance
None
L
X
Input
None
LL
H
L
↑
Input
None
LL
H
↑
Input
Mail2Write
L
H
L
X
Output
None
LH
H
L
↑
Output
FIFO read
L
H
L
H
X
Output
None
LH
H
↑
Output
Mail1 Read (Set
MBF1 HIGH)
TABLE 3 — PORT-B ENABLE FUNCTION TABLE
CSA
W/
RA
ENA
MBA
CLKA
Data A (A0-A35) I/O
Port Functions
H
X
High-Impedance
None
L
H
L
X
Input
None
LH
H
L
↑
Input
FIFO Write
LH
H
↑
Input
Mail1Write
L
X
Output
None
LL
H
L
↑
Output
None
L
H
X
Output
None
LL
H
↑
Output
Mail2 Read (Set
MBF2 HIGH)
TABLE 2 —
—
— PORT-A ENABLE FUNCTION TABLE
TABLE 4 — FIFO FLAG OPERATION (IDT STANDARD AND FWFT MODES)
Synchronized
Number of Words in FIFO
(1,2)
to CLKB
to CLKA
IDT72V3653
(3)
IDT72V3663
(3)
IDT72V3673
(3)
EF/OR
AE
AF
FF/IR
000
L
H
1 to X
H
L
H
(X+1) to [2,048-(Y+1)]
(X+1) to [4,096-(Y+1)]
(X+1) to [8,192-(Y+1)]
H
(2,048-Y) to 2,047
(4,096-Y) to 4,095
(8,192-Y) to 8,191
H
L
H
2,048
4,096
8,192
H
L
NOTES:
1. When a word loaded to an empty FIFO is shifted to the output register, its previous FIFO memory location is free.
2. Data in the output register does not count as a "word in FIFO memory". Since in FWFT mode, the first word written to an empty FIFO goes unrequested to the output register (no
read operation necessary), it is not included in the memory count.
3. X is the Almost-Empty offset used by
AE. Y is the Almost-Full offset used by AF. Both X and Y are selected during a FIFO reset or Port A programming.