NXP Semiconductors MC68HC705B16NCFN

Overview

MC68HC705B16NCFN from Freescale is an 8-bit HCMOS microcontroller featuring 16 KB on-chip ROM, 256 bytes RAM, a 10-bit ADC with 8 input channels, two 16-bit programmable timers with input capture/output compare, and an asynchronous serial communications interface (SCI). It operates at up to 4 MHz with 5 V supply and targets embedded control in automotive body electronics, industrial sensors, and appliance motor control.

For engineers reviewing the MC68HC705B16NCFN datasheet, MC68HC705B16NCFN pinout, MC68HC705B16NCFN application, or MC68HC705B16NCFN equivalent, this page delivers verified technical context, package mapping, functional specifications, and real-world implementation guidance for legacy system maintenance and drop-in replacement design.

Technical Context

The MC68HC705B16NCFN implements the M68HC05 CPU core with 32 instruction mnemonics, direct/extended/indexed addressing modes, and condition-code register (CCR)–based branching. Its memory map includes 16 KB ROM (mask-programmed), 256 B RAM, and dedicated I/O register space mapped to addresses $0000–$00FF.

Peripheral integration includes a 10-bit successive-approximation ADC with software-selectable reference (V_RL/V_RH), dual 16-bit timer modules supporting input capture (ICR1/ICR2), output compare (OCR1/OCR2), and pulse-length modulation (PLMA/PLMB), plus an SCI compatible with RS-232 framing using RDI/TDO/SCLK pins.

Key Specifications

Pinout & Package

MC68HC705B16NCFN is housed in a 56-pin Shrink Dual In-Line Package (SDIP) with 0.3-inch body width and 0.1-inch lead pitch. The package supports through-hole mounting and meets JEDEC MS-012 standards for thermal and mechanical reliability in industrial environments.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705B16CDW, MC68HC705B16NCFN offers drop-in compatibility with existing SDIP layouts, while MC68HC705B16NCFE extends operational range without changing hardware design - making the NCFN variant optimal for cost-sensitive, volume-manufactured control units.

Availability

MC68HC705B16NCFN is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, home appliance motor control, and legacy PLC retrofit projects requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705B16NCFN 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 U.S.-based semiconductor company specializing in embedded processors, analog, and mixed-signal ICs for automotive, industrial, and consumer markets.

The MC68HC705B16NCFN belongs to the M68HC05 family - a line of cost-optimized, mask-ROM-based 8-bit microcontrollers designed for high-volume, resource-constrained embedded control applications with minimal external components.

FAQ

What is the maximum operating frequency of the MC68HC705B16NCFN?

The MC68HC705B16NCFN operates at a maximum bus frequency of 4 MHz, corresponding to a 4 MHz crystal or external clock applied to the OSC1 pin. This yields approximately 2 million instructions per second (MIPS) execution speed, sufficient for real-time control tasks such as motor commutation and sensor polling. The internal clock divider is fixed, so no PLL or frequency multiplication is available. All timing parameters in the datasheet assume operation at this rated frequency.

Does the MC68HC705B16NCFN include on-chip EEPROM?

No, the MC68HC705B16NCFN does not contain physical EEPROM. It features 16 KB of mask-programmed ROM and 256 bytes of RAM. However, it supports EEPROM emulation using designated ROM pages and RAM variables, enabling nonvolatile storage of calibration data or user settings through software routines. This approach avoids external EEPROM but requires careful wear-leveling implementation by the firmware developer.

Can the MC68HC705B16NCFN's ADC measure negative voltages?

No, the MC68HC705B16NCFN's 10-bit ADC is single-ended and referenced to V_RL (typically VSS) and V_RH (typically VDD). It accepts only positive input voltages within the 0 V to VDD range. Inputs below VSS or above VDD risk damage or erroneous conversion. For bipolar signal conditioning, external op-amp circuitry must shift and scale the input to fit within the 0–5 V window before connection to PD0–PD7.

What debug or programming interface does the MC68HC705B16NCFN support?

The MC68HC705B16NCFN lacks on-chip debug interfaces like BDM or JTAG. Programming is performed via mask ROM at fabrication - no field reprogramming is possible. Development relies on EPROM-based variants (e.g., MC68HC705B16CDW) with UV-erasable windows or third-party emulators that replicate the MC68HC05 bus timing. Final firmware is validated using ROM checksums and self-test routines built into the mask image.

Is the MC68HC705B16NCFN RoHS compliant?

MC68HC705B16NCFN was manufactured prior to RoHS Directive enforcement and uses leaded solder in its SDIP package. It is not RoHS compliant. For new designs requiring compliance, NXP recommends migration paths such as the S08QG series or Kinetis E-series microcontrollers, which offer pin-compatible peripheral sets and modern toolchain support while meeting current environmental regulations.