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
APRIL 3, 2006
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
EF
s and ORing of all
FF
s (i.e. all
must be set to generate the correct composite
FF
or
EF
). See Figure 14.
5. The Retransmt (
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