9
COMMERCIAL, INDUSTRIAL AND MILITARY
TEMPERATURE RANGES
IDT7203/7204/7205/7206/7207/7208 CMOS ASYNCHRONOUS FIFO
2,048 x 9, 4,096 x 9, 8,192 x 9, 16,384 x 9, 32,768 x 9 and 65,536 x 9
Figure 9. Half-Full Flag Timing
Figure 10. Expansion Out
Figure 11. Expansion In
OPERATING MODES:
Care must be taken to assure that the appropriate flag is monitored by
each system (i.e. FF is monitored on the device where W is used; EF is monitored
on the device where R is used). For additional information on the IDT7203/7204/
7205/7206/7207, refer to Tech Note 8: Operating FIFOs on Full and Empty
Boundary Conditions and Tech Note 6: Designing with FIFOs.
Single Device Mode
A single IDT7203/7204/7205/7206/7207/7208 may be used when the
application requirements are for 2,048/4,096/8,192/16,384/32,768/65,536 words
or less. These FIFOs are in a Single Device Configuration when the Expansion
In (XI) control input is grounded (see Figure 12).
Depth Expansion
These FIFOs can easily be adapted to applications when the require-
ments are for greater than 2,048/4,096/8,192/16,384/32,768/65,536 words.
Figure 14 demonstrates Depth Expansion using three IDT7203/7204/7205/
7206/7207/7208s. Any depth can be attained by adding additional IDT7203/
7204/7205/7206/7207/7208s. These devices operate in the Depth Expansion
mode when the following conditions are met:
1. The first device must be designated by grounding the First Load (FL) control
input.
2. All other devices must have FL in the HIGH state.
3. The Expansion Out (XO) pin of each device must be tied to the Expansion
In (XI) pin of the next device. See Figure 14.
4. External logic is needed to generate a composite Full Flag (FF) and Empty
Flag (EF). This requires the ORing of all EFs and ORing of all FFs (i.e. all
must be set to generate the correct composite FF or EF). See Figure 14.
5. The Retransmit (RT) function and Half-Full Flag (HF) are not available in
the Depth Expansion Mode.
For additional information on the IDT7203/7204/7205/7206/7207, refer to
Tech Note 9: Cascading FIFOs or FIFO Modules.
W
R
HF
HALF-FULL OR LESS
MORE THAN HALF-FULL
HALF-FULL OR LESS
t
RHF
t
WHF
2661 drw11
W
R
XO
WRITE TO
LAST PHYSICAL
LOCATION
t
XOL
t
XOH
READ FROM
LAST PHYSICAL
LOCATION
2661 drw12
t
XOH
t
XOL
W
R
XI
WRITE TO
FIRST PHYSICAL
LOCATION
READ FROM
FIRST PHYSICAL
LOCATION
t
XI
t
XIR
2661 drw13
t
XIS
t
XIS
