L8C201/202/203/204
DEVICES INCORPORATED
512/1K/2K/4K x 9-bit Asynchronous FIFO
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).
5. The Retransmit (RT) function and
Half-Full Flag (HF) are not avail-
able in the Depth Expansion Mode.
Bidirectional Mode
OPERATING MODES
Single Device Mode
A single FIFO may be used when the
application requirements are for the
number of words in a single device.
The FIFOs are in a Single Device
Configuration when the Expansion In
(XI) control input is grounded. In this
mode the Half-Full Flag (HF), which is
an active-low output, is the active
function of the combination pin XO/
HF.
The FIFOs can easily be adapted to
applications where the requirements
are for greater than the number of
words in a single device. Any depth
can be attained by adding additional
FIFOs. The FIFOs operates in the
Depth Expansion configuration when
the following conditions are met:
1. The first device must be designated
by grounding the First Load (FL)
control input.
O
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 with the last device connect-
ing back to the first.
BS
O
FIFO Products
3
03/04/99–LDS.8C201/2/3/4-H
Depth Expansion (Daisy Chain) Mode
LE
Applications which require data
buffering between two systems (each
system capable of read and write
Width Expansion Mode
operations) can be achieved by pairing
Word width may be increased simply FIFOs. Care must be taken to assure
by connecting the corresponding input that the appropriate flag is monitored
control signals of multiple devices.
by each system (i.e., FF is monitored
Status flags (EF, FF, and HF) can be
on the device when W is used; EF is
detected from any one device. Any
monitored on the device when R is
word width can be attained by adding used). Both Depth Expansion and
additional FIFOs. Flag detection is
Width Expansion may be used in this
accomplished by monitoring the FF,
mode.
EF, and HF signals on either (any)
device used in the width expansion
configuration.
Do not connect any
output signals together.
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LOGIC [ LOGIC DEVICES INCORPORATED ]
