Renesas CS80C286-12

Overview

CS80C286-12 from Intersil is a static CMOS 16-bit microprocessor with integrated memory management unit (MMU), supporting real and protected virtual address modes, 12.5 MHz maximum clock frequency, 16 MB physical / 1 GB virtual address space per task, and compatibility with 80C86/80C88 software - used in industrial control systems requiring deterministic multi-tasking and memory isolation.

For engineers reviewing the CS80C286-12 datasheet, CS80C286-12 pinout, CS80C286-12 application, or CS80C286-12 equivalent, key selection considerations include its static CMOS operation enabling DC-to-12.5 MHz clock flexibility, bus cycle timing for legacy ISA-compatible designs, power consumption at 220 mA max under active load, and PLCC-68 packaging for through-hole or surface-mount retrofits.

Technical Context

The CS80C286-12 implements a segmented memory architecture with four 16-bit segment registers (CS, DS, SS, ES), a 16-bit instruction pointer, and status/control registers including the Machine Status Word (MSW) with Protection Enable (PE) bit. Its execution unit supports a superset of the 80C86/80C88 instruction set, including task-switching instructions like LMSW/SMSW and ESC for coprocessor extension.

It operates in two distinct modes: Real Address Mode (1 MB address space, object-code compatible with 80C86) and Protected Virtual Address Mode (16 MB physical / 1 GB virtual per task, hardware-enforced memory protection via descriptor tables). Bus interface uses multiplexed 24-bit address (A23–A0) and 16-bit data (D15–D0) with BHE/A0 encoding for byte/word transfers and status signals S0/S1/M/IO/COD/INTA to decode cycle type.

Key Specifications

Pinout & Package

CS80C286-12 is supplied in a 68-pin Plastic Leaded Chip Carrier (PLCC) package, pin-compatible with other 80C286 variants in the same PLCC-68 footprint (N68.95), suitable for socketed or reflow-soldered industrial control boards.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 16-bit microprocessor applications.

Compared with CS80C286-12, IS80C286-12 offers extended thermal resilience without performance trade-offs, while CG80C286-12 provides mechanical interchangeability in PGA-based legacy platforms - neither is pin-compatible with CS80C286-12 due to differing package types and land patterns.

Availability

CS80C286-12 is available at Aetrix Electronics and suitable for industrial control systems, avionics subsystems, and ruggedized communications equipment requiring stable component supply across long-lifecycle programs.

Supply support for CS80C286-12 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Intersil Corporation was a U.S.-based semiconductor manufacturer specializing in high-reliability analog and mixed-signal ICs, later acquired by Renesas Electronics in 2017.

The 80C286 product line was designed for embedded computing applications demanding memory protection, multi-tasking capability, and backward compatibility with 8086-era software - targeting industrial, medical, and defense systems where long-term availability and deterministic behavior were critical.

FAQ

What is the maximum operating frequency of the CS80C286-12?

The CS80C286-12 is rated for a maximum clock frequency of 12.5 MHz, as confirmed in the Intersil FN2947 datasheet Rev.3.00. This specification defines the upper limit for reliable instruction execution and bus timing compliance. Exceeding this frequency may result in undefined behavior or timing violations. The CS80C286-12 supports static CMOS operation, meaning it can also run at lower frequencies-including DC-without loss of state.

Does the CS80C286-12 support the 80287 numeric coprocessor?

Yes, the CS80C286-12 is explicitly compatible with the 80287 numeric data coprocessor, as stated in the "Features" section of the FN2947 datasheet. It uses the PEREQ (Processor Extension Request) and PEACK (Processor Extension Acknowledge) signals to coordinate operand transfers. The CS80C286-12 handles coprocessor instruction decoding and exception signaling, allowing seamless floating-point acceleration without software emulation overhead.

What package type is used for the CS80C286-12?

The CS80C286-12 is supplied in a 68-pin Plastic Leaded Chip Carrier (PLCC) package, identified by package code N68.95 in the Ordering Information table. This surface-mount or socket-compatible package features a J-lead configuration and is distinct from the PGA variant (G68.B). The PLCC form factor supports reflow soldering and is commonly used in industrial PCBs where mechanical robustness and thermal cycling resistance are required.

How does memory protection work on the CS80C286-12?

The CS80C286-12 implements hardware-enforced memory protection via its integrated Memory Management Unit (MMU), which supports four privilege levels (rings 0–3) and descriptor-based segmentation. In Protected Virtual Address Mode, access checks occur on every memory reference using segment descriptors stored in descriptor tables. Violations trigger exceptions such as General Protection Fault (GP#), preventing unauthorized code or data access. This mechanism is intrinsic to the CS80C286-12 silicon and requires no external logic.

Is the CS80C286-12 pin-compatible with other 80C286 speed grades in PLCC packaging?

Yes, the CS80C286-12 is fully pin-compatible with other PLCC-packaged 80C286 variants including CS80C286-16, CS80C286-20, and CS80C286-25. All share identical pin count (68), pinout arrangement, signal definitions, and electrical interface characteristics. The only differences are maximum clock rating and corresponding active current specifications - allowing direct substitution in designs where timing margins permit.