NXP Semiconductors MC68302FC20C

Overview

MC68302FC20C from Freescale Semiconductor is a single-chip integrated multi-protocol processor combining an MC68000/MC68008 microprocessor core, a System Integration Block (SIB), and a Communications Processor (CP). It operates at 20 MHz, integrates 1152 bytes of on-chip dual-port RAM, supports HDLC/SDLC, UART, Bisync, DDCMP, and Totally Transparent protocols via three SCCs, and targets ISDN terminal adapters and data concentrators.

For engineers reviewing the MC68302FC20C datasheet, MC68302FC20C pinout, MC68302FC20C application, or MC68302FC20C equivalent, key selection criteria include its 20 MHz clock speed, triple SCC with protocol flexibility, dual-port RAM size, interrupt controller modes, and TQFP-132 package compatibility for legacy telecom hardware integration.

Technical Context

The MC68302FC20C implements a tightly coupled architecture where the MC68000/MC68008 core handles general-purpose execution while a dedicated RISC-based Communications Processor manages serial protocol processing independently. Its SIB provides bus arbitration, DRAM refresh, IDMA, three timers (including watchdog), and four programmable chip-select lines with wait-state logic.

Three full-duplex Serial Communication Controllers (SCCs) support concurrent HDLC/SDLC, UART, Bisync, DDCMP, and Totally Transparent operation, each backed by six serial DMA channels and eight-buffer frame handling without CPU intervention. Two Serial Management Controllers (SMCs) interface with IDL and GCI physical layers, enabling inter-chip digital link and general circuit interface connectivity.

Key Specifications

Pinout & Package

MC68302FC20C is housed in a 132-pin Thin Quad Flat Pack (TQFP) package with 0.4 mm lead pitch and 20 mm × 20 mm body size. Pin assignments follow Motorola/Freescale standard layout for MC68302 derivatives, supporting 16-bit data bus, 24-bit address bus, and dedicated SCC/SMC I/O groups.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multi-protocol communications processor applications.

Compared with MC68LC302RC25 and MC68EN302EC33, the MC68302FC20C offers optimal balance of protocol breadth, deterministic real-time response, and legacy pinout compatibility-making it the preferred choice for retrofitting existing ISDN and concentrator designs without board rework.

Availability

MC68302FC20C is available at Aetrix Electronics and suitable for ISDN terminal adapters, data concentrators, and legacy telecom line cards requiring stable component supply and long-term obsolescence mitigation.

Supply support for MC68302FC20C 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

Freescale Semiconductor (now part of NXP Semiconductors) was a leading designer of embedded processors and analog/mixed-signal ICs, founded from Motorola's semiconductor division in 2004.

The MC68302 product line was engineered specifically for telecom infrastructure and industrial data communications, emphasizing protocol offload, deterministic interrupt latency, and seamless integration of serial and memory subsystems.

FAQ

What is the maximum operating frequency of the MC68302FC20C?

The MC68302FC20C is rated for a maximum operating frequency of 20 MHz, as confirmed by Freescale's official datasheet revision 3. This speed defines the upper limit for instruction cycle timing, SCC baud rate generation, and system bus bandwidth. Operating beyond 20 MHz may cause timing violations in the MC68000 core or CP subsystem. The MC68302FC20C requires a stable 5 V ±5% supply and external crystal or clock source synchronized to this rating.

Does the MC68302FC20C support V.110 protocol, and how is it implemented?

Yes, the MC68302FC20C supports V.110 protocol through its three Serial Communication Controllers (SCCs), as documented in Freescale Application Note AN1227. V.110 framing is handled in hardware by the SCCs' protocol engines, enabling rate-adaptive asynchronous-to-synchronous conversion for ISDN data services. The MC68302FC20C does not require firmware-based bit-banging; configuration is done via CP register writes to select V.110 mode and set clocking parameters.

How much on-chip memory does the MC68302FC20C integrate, and what is its access architecture?

The MC68302FC20C integrates 1152 bytes of on-chip dual-port static RAM, physically shared between the MC68000 core and Communications Processor. Each port has independent address/data buses and arbitration logic, allowing concurrent read/write operations without contention. This memory is mapped into both CPU and CP address spaces and is used for protocol buffers, descriptor tables, and mailbox communication-critical for low-latency packet processing in the MC68302FC20C.

Is the MC68302FC20C pin-compatible with other MC68302 variants like the MC68302FC25?

Yes, the MC68302FC20C is fully pin-compatible with other MC68302 derivatives in the 132-pin TQFP package, including MC68302FC16, MC68302FC25, and MC68302FC33. All share identical pinout, signal naming, power/ground distribution, and package dimensions. Frequency differences are managed solely by clock source selection and internal PLL configuration-no PCB redesign is needed when upgrading or downgrading speed grades within this family.

What debug features does the MC68302FC20C provide for embedded development?

The MC68302FC20C includes hardware freeze mode, which halts the CPU while allowing continued CP operation for real-time peripheral observation. It also supports background debug mode via BDM interface, enabling breakpoint insertion, register inspection, and memory dump without disrupting SCC/SMC timing. These features are accessible through standard Motorola BDM tools and are fully documented in the MC68302FC20C User's Manual Chapter 9.