FUNCTIONAL DESCRIPTION

The LH5420 contains two FIFO buffers, FIFO #1 and FIFO #2. These operate in parallel, but in opposite directions, for bidirectional data buffering. FIFO #1 and FIFO #2 each are organized as 256 words by 36 bits. The LH5420 is ideal either for wide unidirectional applications or for bidirectional data applications; component count and board area are reduced.

FEATURES

? Fast Cycle Times: 25/30/35 ns

? Two 256 × 36-bit FIFO Buffers

? Full 36-bit Word Width

? Selectable 36/18/9-bit Word Width on Port B

? Independently-Synchronized (‘Fully Asynchronous’) Operation of Port A and Port B

? ‘Synchronous’ Enable-Plus-Clock Control at Both Ports

? R/W, Enable, Request, and Address Control Inputs are Sampled on the Rising Clock Edge

? Synchronous Request/Acknowledge ‘Handshake’ Capability; Use is Optional

? Device Comes Up Into a Known Default State at Reset; Programming is Allowed, but is not Required

? Asynchronous Output Enables

? Five Status Flags per Port: Full, Almost-Full, Half-Full, Almost-Empty, and Empty

? Almost-Full Flag and Almost-Empty Flag are Programmable

? Mailbox Registers with Synchronized Flags

? Data-Bypass Function

? Data-Retransmit Function

? Automatic Byte Parity Checking

? TTL/CMOS-Compatible I/O

? Space-Saving PQFP Package

? PQFP to PGA Package Conversion