10
COMMERCIAL, INDUSTRIAL AND MILITARY
TEMPERATURE RANGES
IDT7201L/7201LA/7202LA CMOS ASYNCHRONOUS FIFO
256 x 9, 512 x 9 and 1,024 x 9
USAGE MODES:
WIDTH EXPANSION
Word width may be increased simply by connecting the corresponding
input control signals of multiple devices. Status flags (EF, FF and HF) can be
detected from any one device. Figure 13 demonstrates an 18-bit word width
by using two IDT7200/7201A/7202As. Any word width can be attained by
adding additional IDT7200/7201A/7202As (Figure 13).
BIDIRECTIONAL OPERATION
Applications which require data buffering between two systems (each
system capable of Read and Write operations) can be achieved by pairing
IDT7200/7201A/7202As as shown in Figure 16. Both Depth Expansion and
Width Expansion may be used in this mode.
DATA FLOW-THROUGH
Two types of flow-through modes are permitted, a read flow-through
and write flow-through mode. For the read flow-through mode (Figure 17),
the FIFO permits a reading of a single word after writing one word of data into
an empty FIFO. The data is enabled on the bus in (tWEF + tA) ns after the rising
edge of W, called the first write edge, and it remains on the bus until the R line
is raised from LOW-to-HIGH, after which the bus would go into a three-state
mode after tRHZ ns. The EF line would have a pulse showing temporary
deassertion and then would be asserted.
In the write flow-through mode (Figure 18), the FIFO permits the writing
of a single word of data immediately after reading one word of data from a
full FIFO. The R line causes the FF to be deasserted but the W line being LOW
causes it to be asserted again in anticipation of a new data word. On the rising
edge of W, the new word is loaded in the FIFO. The W line must be toggled
when FF is not asserted to write new data in the FIFO and to increment the write
pointer.
COMPOUND EXPANSION
The two expansion techniques described above can be applied together
in a straightforward manner to achieve large FIFO arrays (see Figure 15).
Figure 13. Block Diagram of 256 x 18, 512 x 18, 1,024 x 18 FIFO Memory Used in Width Expansion Mode
Figure 12. Block Diagram of Single 256 x 9, 512 x 9, 1,024 x 9 FIFO
WRITE (W)
DATA IN (D)
FULL FLAG (FF)
RESET (RS)
9
READ (R)
9
DATA OUT (Q)
EMPTY FLAG (EF)
RETRANSMIT (RT)
EXPANSION IN (XI)
(HF)
IDT
7200/
7201A/
7202A
(HALF-FULL FLAG)
2679 drw 14
IDT
7200/
7201A/
7202A
XI XI
9918
9
18
HF
HF
9
DATA
WRITE (W)
FULL FLAG (FF)
RESET (RS)
(D)
IN
READ (R)
EMPTY FLAG (EF)
RETRANSMIT (RT)
DATA
OUT
(Q)
IDT
7200/
7201A/
7202A
2679 drw 15
