11
COMMERCIALTEMPERATURERANGE
IDT72V3624/72V3634/72V3644 3.3V CMOS SyncBiFIFOTM WITH BUS-MATCHING
256 x 36 x 2, 512 x 36 x 2, 1,024 x 36 x 2
SPM
FS1/
SEN
FS0/SD
MRS1
MRS2
X1 AND Y1 REGlSTERS(1)
X2 AND Y2 REGlSTERS(2)
HH
H
↑
X64
X
HH
H
↑↑
64
HH
L
↑
X16
X
HH
L
↑↑
16
HL
H
↑
X8
X
HL
H
↑↑
88
HL
L
↑↑
Parallel programming via Port A
LH
L
↑↑
Serial programming via SD
LH
H
↑↑
Reserved
LL
H
↑↑
Reserved
LL
L
↑↑
Reserved
labeled Y2. The index of each register name corresponds to its FIFO number.
TheoffsetregisterscanbeloadedwithpresetvaluesduringtheresetofaFIFO,
programmed in parallel using the FIFO’s Port A data inputs, or programmed
in serial using the Serial Data (SD) input (see Table 1).
SPM,FS0/SD,andFS1/SENfunctionthesamewayinbothIDTStandard
and FWFT modes.
— PRESET VALUES
ToloadaFIFO’sAlmost-EmptyflagandAlmost-FullflagOffsetregisterswith
oneofthethreepresetvalueslistedinTable1,theSerialProgramMode(
SPM)
andatleastoneoftheflag-selectinputsmustbeHIGHduringtheLOW-to-HIGH
transition of its Master Reset input (
MRS1, MRS2). For example, to load the
preset value of 64 into X1 and Y1,
SPM, FS0 and FS1 must be HIGH when
FlFO1reset(
MRS1)returnsHIGH.Flag-offsetregistersassociatedwithFIFO2
are loaded with one of the preset values in the same way with FIFO2 Master
Reset(
MRS2),toggledsimultaneouslywithFIFO1MasterReset(MRS1).For
relevant preset value loading timing diagram, see Figure 3.
— PARALLEL LOAD FROM PORT A
To program the X1, X2, Y1, and Y2 registers from Port A, perform a Master
Reset on both FlFOs simultaneously with
SPMHIGHandFS0andFS1LOW
during the LOW-to-HIGH transition of
MRS1 and MRS2. After this reset is
complete, the first four writes to FIFO1 do not store data in the RAM but load
the offset registers in the order Y1, X1, Y2, X2. The Port A data inputs used by
the offset registers are (A7-A0), (A8-A0), or (A9-A0) for the IDT72V3624,
IDT72V3634, or IDT72V3644, respectively. The highest numbered input is
used as the most significant bit of the binary number in each case. Valid
programming values for the registers range from 1 to 252 for the IDT72V3624;
1 to 508 for the IDT72V3634; and 1 to 1,020 for the IDT72V3644. After all the
offset registers are programmed from Port A, the Port B Full/Input Ready flag
(
FFB/IRB)issetHIGH,andbothFIFOsbeginnormaloperation.RefertoFigure
5foratimingdiagramillustrationofparallelprogrammingoftheflagoffsetvalues.
— SERIAL LOAD
ToprogramtheX1,X2,Y1,andY2registersserially,initiateaMasterReset
with
SPMLOW,FS0/SDLOWandFS1/SENHIGHduringtheLOW-to-HIGH
transitionof
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 32-, 36-, or 40-
bit writes needed to complete the programming for the IDT72V3624,
IDT72V3634, or IDT72V3644, respectively. The four registers are written in
theorderY1,X1,Y2,andfinally,X2. Thefirst-bitwritestoresthemostsignificant
bitoftheY1registerandthelast-bitwritestorestheleastsignificantbitoftheX2
register.Eachregistervaluecanbeprogrammedfrom1to252(IDT72V3624),
1 to 508 (IDT72V3634), or 1 to 1,020 (IDT72V3644).
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 (
FFB/
IRB) flag also remains LOW throughout the serial programming process, until
allregisterbitsarewritten.
FFB/IRBissetHIGHbytheLOW-to-HIGHtransition
ofCLKBafterthelastbitisloadedtoallownormalFIFO2operation.SeeFigure
6 for Serial Programming of the Almost-Full Flag and Almost-Empty Flag
Offset Values (IDT Standard and FWFT Modes) timing diagram.
FIFO WRITE/READ OPERATION
ThestateofthePortAdata(A0-A35)linesiscontrolledbyPortAChipSelect
(
CSA)andPortAWrite/Readselect(W/RA).TheA0-A35linesareintheHigh-
impedance state when either
CSA or W/RA is HIGH. The A0-A35 lines are
active outputs 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
byaLOW-to-HIGHtransitionofCLKAwhen
CSAisLOW,W/RAisLOW,ENA
is HIGH, MBA is LOW, and
EFA/ORAisHIGH(seeTable2).FIFOreadsand
writes on Port A are independent of any concurrent Port B operation.
The Port B control signals are identical to those of Port A with the exception
thatthePortBWrite/Readselect(
W/RB)istheinverseofthePortAWrite/Read
select (W/
RA).ThestateofthePortBdata(B0-B35)linesiscontrolledbythe
Port B Chip Select (
CSB) and Port B Write/Read select (W/RB). The B0-B35
lines are in the high-impedance state when either
CSB is HIGH or W/RB is
NOTES:
1. X1 register holds the offset for
AEB; Y1 register holds the offset for AFA.
2. X2 register holds the offset for
AEA; Y2 register holds the offset for AFB.
TABLE 1 — FLAG PROGRAMMING