IDT72125_16 Datasheet, PDF (8/11 Pages) Integrated Device Technology – CMOS PARALLEL-TO-SERIAL FIFO

IDT72125 PARALLEL-TO-SERIAL CMOS FIFO
1,024 x 16
RS
SOCP
FL/DIR
tFLS
tFLH
RSOX
RSIX
Figure 9. Serial Read Expansion
COMMERCIAL TEMPERATURE RANGE
15
tDIRS
0
tDIRH
tSOXD1
tSOXD2
tSIXS
tRSIXPW
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OPERATING CONFIGURATIONS
SINGLE DEVICE MODE
The device must be reset before beginning operation so that all flags are
set to location zero. In the standalone case, the RSIX line is tied HIGH and
indicates single device operation to the device. The RSOX/AEF pin defaults to
AEF and outputs the Almost-Empty and Almost-Full Flag.
WIDTH EXPANSION MODE
In the cascaded case, word widths of more than 16 bits can be achieved
by using more than one device. By tying the RSOX and RSIX pins together,
as shown in Figure 11, and programming which is the Least Significant Device,
a cascaded serial word is achieved. The Least Significant Device is pro-
grammed by a LOW on the FL/DIR pin during reset. All other devices should
be programmed HIGH on the FL/DIR pin at reset.
VCC
SERIAL OUTPUT CLOCK
PARALLEL DATA IN
RSIX
SOCP
D0-15
RSOX/AEF
SO
Figure 10. Single Device Configuration
ALMOST-EMPTY/FULL FLAG
SERIAL DATA OUT
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TABLE 1 — RESET AND FIRST LOAD TRUTH TABLE-
SINGLE DEVICE CONFIGURATION
Inputs
Internal Status
Outputs
Mode
RS
FL
DIR
Read Pointer
Write Pointer
AEF, EF
FF
HF
Reset
Read/Write
0
X
X
Location Zero
Location Zero
0
1
1
(1)
(1)
1
X
0,1
Increment
Increment
X
X
X
NOTE:
1. Pointer will increment if appropriate flag is HIGH
The Serial Data Output (SO) of each device in the serial word must be tied
together. Since the SO pin is three stated, only the device which is currently
shifting out is enabled and driving the 1-bit bus. NOTE: After reset, the level on
the FL/DIR pin decides if the Least Significant or Most Significant Bit is read first
out of each device.
The three flag outputs, Empty (EF), Half-Full (HF) and Full (FF), should
be taken from the Most Significant Device (in the example, FIFO #2). The
Almost-Empty/Almost-Full flag is not available. The RSOX pin is used for
expansion.
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