24
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72261LA/72271LA SuperSync FIFO™
16,384 x 9 and 32,768 x 9
NOTES:
1. Use an AND gate in IDT Standard mode, an OR gate in FWFT mode.
2. Do not connect any output control signals directly together.
3. FIFO #1 and FIFO #2 must be the same depth, but may be different word widths.
OPTIONAL CONFIGURATIONS
WIDTH EXPANSION CONFIGURATION
Word width may be increased simply by connecting together the control
signals of multiple devices. Status flags can be detected from any one device.
The exceptions are the EF and FF functions in IDT Standard mode and the
IR and OR functions in FWFT mode. Because of variations in skew between
RCLK and WCLK, it is possible for EF/FF deassertion and IR/OR assertion
to vary by one cycle between FIFOs. In IDT Standard mode, such problems
Figure 19. Block Diagram of 16,384 x 18 and 32,768 x 18 Width Expansion
WRITE CLOCK (WCLK)
m + n m n
MASTER RESET (MRS)
READ CLOCK (RCLK)
DATA OUT
n
m + n
WRITE ENABLE (WEN)
FULL FLAG/INPUT READY (FF/IR)
PROGRAMMABLE (PAF)
PROGRAMMABLE (PAE)
EMPTY FLAG/OUTPUT READY (EF/OR) #2
OUTPUT ENABLE (OE)
READ ENABLE (REN)
m
LOAD (LD)
IDT
72261LA
72271LA
EMPTY FLAG/OUTPUT READY (EF/OR) #1
PARTIAL RESET (PRS)
IDT
72261LA
72271LA
4671 drw 22
FULL FLAG/INPUT READY (FF/IR) #2
HALF-FULL FLAG (HF)
FIRST WORD FALL THROUGH/
SERIAL INPUT (FWFT/SI)
RETRANSMIT (RT)
#1
FIFO
#2
GATE
(1)
GATE
(1)
D
0
- Dm
DATA IN
Dm
+1
- Dn
Q
0
- Qm
Qm
+1
- Qn
FIFO
#1
can be avoided by creating composite flags, that is, ANDing EF of every FIFO,
and separately ANDing FF of every FIFO. In FWFT mode, composite flags
can be created by ORing OR of every FIFO, and separately ORing IR of every
FIFO.
Figure 21 demonstrates a width expansion using two IDT72261LA/
72271LA devices. D0 - D8 from each device form a 18-bit wide input bus and
Q0-Q8 from each device form a 18-bit wide output bus. Any word width can
be attained by adding additional IDT72261LA/72271LA devices.
