TI SN74ACT7808-40 PAG

A FIFO memory is a storage device that allows data to be written to and read from its array at independent data rates. The SN74ACT7808 is a 2048-word × 9-bit FIFO designed for high-speed operation and fast access times. It processes data in bit-parallel format at data rates up to 50 MHz with 15 ns access time.

Data is written to memory on the low-to-high transition at the load clock (LDCK) input, and read out on the low-to-high transition at the unload clock (UNCK) input. The memory is full when the number of words written exceeds the number of words read by 2048. When the memory is full, the LDCK signal has no effect on data in the memory. When the memory is empty, the UNCK signal has no effect on data in the memory.

The status of the FIFO memory is monitored by the full (FULL), empty (EMPTY), half-full (HF), and almost-full/almost-empty (AF/AE) flags. The FULL output is active low when the memory is full, and high when the memory is not full. The EMPTY output is active low when the memory is empty, and high when the memory is not empty. The HF output is high when the FIFO contains 1024 or more words, and low when the FIFO contains 1023 or fewer words. The AF/AE status flag is a programmable flag. If program enable (PEN) is low, the first or second low-to-high transition of LDCK after reset can be used to program the almost-empty offset value (X) and the almost-full offset value (Y). The AF/AE flag is high when the FIFO contains X or fewer words or (2048 – Y) or more words. The AF/AE flag is low when the FIFO contains (X + 1) to (2047 – Y) words.

A low level on the reset (RESET) input resets the internal stack pointer and sets FULL high, AF/AE high, HF low, and EMPTY low. The Q outputs are not reset to any particular logic level.

When the first word is loaded into an empty memory, EMPTY goes high and data appears on the Q outputs. Note that the first word need not be unloaded. Data outputs are non-inverting with respect to data inputs, and are in a high-impedance state when the output enable (OE) input is low. OE does not affect the output flags.

Cascading in both word-width and word-depth directions is straightforward. If the FIFO is not used for depth expansion, cascade enable (CASEN) must be connected high.

The FIFO must be reset upon power-up.

The SN74ACT7808 operates over a temperature range of 0°C to 70°C.