13
COMMERCIALTEMPERATURERANGE
IDT72V3656/72V3666/72V3676 3.3V CMOS TRIPLE BUS SyncFIFOTM
WITH BUS MATCHING 2,048 x 36 x 2, 4,096 x 36 x 2 and 8,192 x 36 x 2
CSA
W/
RA
ENA
MBA
CLKA
LOOP
Data A(A0-A35) I/O
PORT FUNCTION
H
X
H
High-Impedance
None
L
H
L
X
H
Input
None
LH
H
L
↑
H
Input
FIFO1 write
LH
H
↑
H
Input
Mail1 write
L
X
H
Output
None
LL
H
L
↑
H
Output
FIFO2 read
L
H
X
H
Output
None
LL
H
↑
H
Output
Mail2 read (set
MBF2 HIGH)
LH
H
L
↑
L
Output
Loop the data output of FIFO2 to input
of FIFO1 only
LL
H
L
↑
L
Output
Loop the data output of FIFO2 to input
of FIFO1 and put data on Port A
CSB
RENB
MBB
CLKB
Data B (B0-B17) Outputs
PORT FUNCTION
H
X
High-Impedance
None
L
X
Output
None
LH
L
↑
Output
FIFO1 read
L
H
X
Output
None
LH
H
↑
Output
Mail1 read (set
MBF1 HIGH)
TABLE 4
PORT C ENABLE FUNCTION TABLE
TABLE 3
PORT B ENABLE FUNCTION TABLE
WENC
MBC
CLKC
Data C (C0-C17) Inputs
PORT FUNCTION
HL
↑
Input
FIFO2 write
HH
↑
Input
Mail2 write
L
X
Input
None
L
H
X
Input
None
INTERSPERSED PARITY
Interspersed Parity is selected during a Master Reset of the FIFO. Refer to
Table 1 for the set-up configuration of Interspersed Parity. The Interspersed
Parity function allows the user to select the location of the parity bits in the word
loaded into the parallel port (A0-An) during programming of the flag offset
values. If Interspersed Parity is selected then during parallel programming of
the flag offset values, the device will ignore data line A8. If Non-Interspersed
ParityisselectedthendatalineA8willbecomeavalidbit.IfInterspersedParity
isselectedserialprogrammingoftheoffsetvaluesisnotpermitted,onlyparallel
programming can be done.
— SERIAL LOAD
ToprogramtheX1,X2,Y1,andY2registersserially,initiateaMasterReset
with FS2 LOW, FS0/SD LOW and FS1/
SEN HIGH during the LOW-to-HIGH
transition of
MRS1andMRS2.Afterthisresetiscomplete,theXandYregister
values are loaded bit-wise through the FS0/SD input on each LOW-to-HIGH
transition of CLKA that the FS1/
SEN input is LOW. There are 44-, 48-, or 52-
bitwritesneededtocompletetheprogrammingfortheIDT72V3656,IDT7V3666,
or IDT72V3676, respectively. The four registers are written in the order Y1,
X1, Y2 and finally, X2. The first-bit write stores the most significant bit of the Y1
registerandthelast-bitwritestorestheleastsignificantbitoftheX2register.Each
register value can be programmed from 1 to 2,044 (IDT72V3656), 1 to 4,092
(IDT72V3666), or 1 to 8,188 (IDT72V3676).
When the option to program the Offset registers serially is chosen, the Port
AFull/InputReady(
FFA/IRA)flagremainsLOWuntilallregisterbitsarewritten.
FFA/IRAissetHIGHbytheLOW-to-HIGHtransitionofCLKAafterthelastbit
is loaded to allow normal FIFO1 operation. The Port B Full/Input Ready (
FFC/
IRC) flag also remains LOW throughout the serial programming process, until
allregisterbitsarewritten.
FFC/IRCissetHIGHbytheLOW-to-HIGHtransition
of CLKC after the last bit is loaded to allow normal FIFO2 operation.
See Figure 9 timing diagram, Serial Programming of the Almost-Full Flag
and Almost-Empty Flag Offset Values after Reset (IDT Standard and FWFT
Modes).
FIFO WRITE/READ OPERATION
The state of the Port A data (A0-A35) outputs is controlled by Port A Chip
Select (
CSA)andPortAWrite/ReadSelect(W/RA).TheA0-A35outputsare
in the high-impedance state when either
CSA or W/RA is HIGH. The A0-A35
outputs are active when both
CSA and W/RA are LOW.
Data is loaded into FIFO1 from the A0-A35 inputs on a LOW-to-HIGH
transition of CLKA when
CSA is LOW, W/RA is HIGH, ENA is HIGH, MBA is
LOW, and
FFA/IRA is HIGH. Data is read from FIFO2 to the A0-A35 outputs
by a LOW-to-HIGH transition of CLKA when
CSAisLOW,W/RAisLOW,ENA
is HIGH, MBA is LOW, and
EFA/ORA is HIGH (see Table 2). FIFO reads and
writes on Port A are independent of any concurrent Port B or Port C
operation.
TABLE 2
PORT A ENABLE FUNCTION TABLE