Datasheet

SN74ALVC7804
512 × 18
FIRST-IN, FIRST-OUT MEMORY
SCAS432 – JANUARY 1995
3
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
functional block diagram
Q0–Q17
AF/AE
HF
OE
D0–D17
UNCK
LDCK
RESET
PEN
EMPTY
FULL
Status-
Flag
Logic
Read
Pointer
Reset
Logic
512 × 18
Write
Pointer
RAM
Terminal Functions
TERMINAL
I/O
DESCRIPTION
NAME NO.
I/O
DESCRIPTION
AF/AE 24 O
Almost full/almost empty flag. Depth offset values can be programmed for AF/AE, or the default
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.
D0–D17
21–14, 12–11,
9–2
I 18-bit data input port
EMPTY 29 O Empty flag. EMPTY is low when the FIFO is empty. A FIFO reset also causes EMPTY to go low.
FULL 28 O Full flag. FULL is low when the FIFO is full. A FIFO reset causes FULL to go high.
HF 22 O Half-full flag. HF is high when the FIFO memory contains 256 or more words. HF is low after reset.
LDCK 25 I Load clock. Data is written to the FIFO on the rising edge of LDCK when FULL is high.
OE 56 I Output enable. When OE is high, the data outputs are in the high-impedance state.
PEN 23 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.
Q0–Q17
33–34, 36–38,
40–43, 45–49,
51, 53–55
O 18-bit data output port
RESET 1 I
Reset. A low level on RESET resets the FIFO and drives AF/AE and FULL high and HF and
EMPTY
low.
UNCK 32 I Unload clock. Data is read from the FIFO on the rising edge of UNCK when EMPTY is high.