SN74ALVC7804_07 Datasheet, PDF (3/13 Pages) Texas Instruments – 512 × 18 FIRST-IN, FIRST-OUT MEMORY

functional block diagram
OE
D0 – D17
UNCK
Read
Pointer
LDCK
Write
Pointer
SN74ALVC7804
512 × 18
FIRST-IN, FIRST-OUT MEMORY
SCAS432 – JANUARY 1995
RAM
512 × 18
RESET
PEN
Reset
Logic
Status-
Flag
Logic
Q0 – Q17
EMPTY
FULL
HF
AF/AE
Terminal Functions
TERMINAL
NAME
NO.
AF/AE
24
D0 – D17
EMPTY
FULL
HF
LDCK
OE
21 – 14, 12 – 11,
9–2
29
28
22
25
56
PEN
23
Q0 – Q17
33 – 34, 36 – 38,
40 – 43, 45 – 49,
51, 53 – 55
RESET
1
UNCK
32
I/O
DESCRIPTION
Almost full/almost empty flag. Depth offset values can be programmed for AF/AE, or the default
O
value of 64 can be used for both the almost empty offset (X) and the almost full offset (Y). AF/AE
is high when memory contains X or less words or (512 – Y) or more words. AF/AE is high after
reset.
I 18-bit data input port
O Empty flag. EMPTY is low when the FIFO is empty. A FIFO reset also causes EMPTY to go low.
O Full flag. FULL is low when the FIFO is full. A FIFO reset causes FULL to go high.
O Half-full flag. HF is high when the FIFO memory contains 256 or more words. HF is low after reset.
I Load clock. Data is written to the FIFO on the rising edge of LDCK when FULL is high.
I Output enable. When OE is high, the data outputs are in the high-impedance state.
I
Program enable. After reset and before the first word is written to the FIFO, the binary value on
D0 – D7 is latched as an AF/AE offset value when PEN is low and WRTCLK is high.
O 18-bit data output port
I
Reset. A low level on RESET resets the FIFO and drives AF/AE and FULL high and HF and
EMPTY low.
I Unload clock. Data is read from the FIFO on the rising edge of UNCK when EMPTY is high.
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