SN74AS890GB

The SN74AS890GB is a 14-bit microprogram sequencer from Texas Instruments, the microcode address generator designed to work alongside the SN74AS888 bit-slice processor. In a microprogrammed CPU it produces the stream of next-microinstruction addresses, sequential, branch, and subroutine, that drive the control store, freeing the data-path slices to do arithmetic and logic. The SN74AS888 it partners with is an 8-bit processor slice with a 16-word by 8-bit register file, an 8-bit ALU, and a shifter, cascadable to 16-bit or 32-bit data widths; the AS890 supplies the microcode addressing that steps such a machine through its routines. It is built in Advanced Schottky (AS) bipolar TTL and supplied here in a 68-pin ceramic pin-grid-array (GB) package.

Key Features

• 14-bit microprogram address - generates addresses into a control store up to 14 bits deep for microcoded engines.
• Bit-slice companion - pairs with the SN74AS888 8-bit processor slice to form the control half of a custom CPU.
• Sequencing modes - supports sequential execution, branching, and subroutine-style microcode flow.
• Advanced Schottky TTL - the AS bipolar process targets the high clock rates expected of bit-slice control logic.
• Ceramic PGA - the 68-pin ceramic pin-grid-array package suits sockets and high-reliability builds.
• Matched family timing - built on the same Advanced Schottky process as the AS888 and AS889, so sequencer and slices share consistent switching behavior.

Typical Applications

• Custom microcoded processors - supplying control-store addressing for bit-slice CPUs built from the AS888 family.
• High-speed controllers - sequencing microcode in signal-processing and instrumentation engines.
• Legacy system support - sustaining bit-slice designs that remain in service.

Unique Advantages

• Purpose-built for the AS888 - as the sequencer companion to the AS888 slice, it provides a matched, proven control path for custom processors.
• Deep control store reach - the 14-bit address range supports substantial microcode programs.
• Socketable ceramic package - the PGA format fits high-reliability and field-serviceable assemblies.
• Defined control path - using a dedicated sequencer rather than discrete logic keeps microcode flow predictable and easier to debug in a custom engine.

Why Choose SN74AS890GB?

The SN74AS890GB is the microsequencer to pair with the SN74AS888 when building or maintaining a bit-slice processor, handling microcode address generation while the slices handle the data path. Its 14-bit addressing, Advanced Schottky speed, and ceramic PGA packaging make it a fit for custom high-speed controllers, and it stays important for keeping existing bit-slice systems alive. Because it was designed as the sequencer half of the AS888 family, it drops into those architectures as a known-good control element rather than a part that must be characterized from scratch.

Contact us for pricing, availability, and lead time on the SN74AS890GB, and tell us your system so we can confirm the matching components.