NXP Semiconductors MC68HC705C9ACFB

Overview

MC68HC705C9ACFB from Freescale Semiconductor is a 8-bit HCMOS EPROM-based microcontroller in the M68HC05 family, featuring 15,932 bytes of user EPROM, 352 bytes of RAM, a 16-bit capture/compare timer, asynchronous SCI and synchronous SPI interfaces, and COP watchdog with clock monitor - deployed in industrial control panels requiring deterministic real-time I/O response.

For engineers reviewing the MC68HC705C9ACFB datasheet, MC68HC705C9ACFB pinout, MC68HC705C9ACFB application, or MC68HC705C9ACFB equivalent, key selection considerations include EPROM programmability, dual-configuration support (C9A/C12A), 44-pin PLCC package compatibility, 3.0–5.5 V single-supply operation, and hardware-level security for firmware protection.

Technical Context

The MC68HC705C9ACFB implements the M68HC05 CPU core with accumulator, index register, stack pointer, and condition code register. It supports six addressing modes including inherent, immediate, direct, extended, indexed (no/8-bit/16-bit offset), and relative - enabling compact code for embedded control tasks.

Its memory-mapped I/O architecture provides 31 bidirectional I/O lines across Ports A–D, with Port C7 offering high-current sink/source capability. Configuration is managed via two mask option registers (PBMOR and C12MOR) programmed into EPROM, allowing runtime-selectable emulation of either MC68HC05C9A or MC68HC05C12A behavior.

Key Specifications

Pinout & Package

MC68HC705C9ACFB is housed in a 44-lead Plastic Leaded Chip Carrier (PLCC) package (Case 777-02), with gull-wing leads, JEDEC MO-047 compliant footprint, and 1.27 mm pitch.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microcontroller applications.

Compared with MC68HC705C8ACFB and MC68HC705P6ACFB, the MC68HC705C9ACFB delivers higher memory capacity, full SPI+SCI dual-serial support, and certified COP/clock monitor functionality - making it the only option among the three qualified for safety-critical timing supervision in industrial environments.

Availability

MC68HC705C9ACFB is available at Aetrix Electronics and suitable for industrial motor control, legacy building automation, and embedded test equipment requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705C9ACFB 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 controllers, analog, and RF solutions for automotive, industrial, and consumer markets.

The MC68HC705C9ACFB belongs to the M68HC05 microcontroller family, engineered for cost-sensitive, real-time control applications demanding EPROM-based firmware persistence, hardware watchdog reliability, and minimal external component count.

FAQ

What is the maximum operating frequency of the MC68HC705C9ACFB?

The MC68HC705C9ACFB supports an external crystal or ceramic resonator up to 8 MHz, yielding a maximum internal CPU clock of 4 MHz (via on-chip divide-by-two). Electrical specifications confirm stable operation across the full 3.0–5.5 V supply range at this frequency, with timing margins validated per Rev. 4.1 datasheet Section 12.7.

Does the MC68HC705C9ACFB support in-circuit programming?

No, the MC68HC705C9ACFB uses one-time-programmable EPROM and requires UV erasure for reprogramming. It lacks on-chip flash or ISP capability. Programming is performed externally using a compatible EPROM programmer prior to soldering, with verification via checksum or read-back through the VPP pin sequence defined in Appendix A.

How is the COP watchdog configured on the MC68HC705C9ACFB?

The COP watchdog is enabled and timed via the C9A COP Control Register ($001E) and reset via the C9A COP Reset Register ($001D). Timeout period is software-selectable (256 to 65,536 E-clock cycles), and clock monitor detection triggers automatic reset if OSC1/OSC2 stops - both features active only when configured in MC68HC05C9A mode.

Can the MC68HC705C9ACFB operate from a 3.3 V supply?

Yes, the MC68HC705C9ACFB is fully specified for 3.3 V operation per Section 12.6 of the Rev. 4.1 datasheet, including all I/O thresholds, timing parameters, and current consumption. It maintains full functionality - including SCI, SPI, timer, and COP - across the 3.0–5.5 V range without configuration changes.

What package type does the MC68HC705C9ACFB use, and is it RoHS-compliant?

The MC68HC705C9ACFB uses a 44-lead Plastic Leaded Chip Carrier (PLCC) package (Case 777-02) with gull-wing leads. As a pre-RoHS-era device, it contains leaded solder and is not RoHS-compliant; however, Aetrix Electronics provides full material declaration documentation and supports legacy compliance pathways for industrial redesign projects.