NXP Semiconductors MC68HC908MR32CB

Overview

MC68HC908MR32CB from NXP Semiconductors (formerly Freescale) is an 8-bit HCS08-core microcontroller with 32 KB on-chip FLASH, 1.5 KB RAM, and integrated motor-control PWM with dead-time insertion, ADC (10-bit, 12-channel), SCI, SPI, and dual timer interfaces. It operates at up to 8 MHz bus frequency and supports automotive and industrial motor control applications requiring real-time fault handling and analog feedback.

For engineers reviewing the MC68HC908MR32CB datasheet, MC68HC908MR32CB pinout, MC68HC908MR32CB application, or MC68HC908MR32CB equivalent, key selection criteria include its 48-pin LQFP package, dedicated PWM output pins (PWM1–PWM6), hardware-based fault protection inputs (FAULT1–FAULT4), and integrated PLL clock generator for stable timing in variable-speed motor drives.

Technical Context

The MC68HC908MR32CB implements the HCS08 CPU core with enhanced addressing modes and a 16-bit index register. Its Clock Generator Module includes a crystal oscillator input (OSC1/OSC2), PLL with programmable bandwidth, and CGMXCLK output for synchronous peripheral operation.

The Pulse-Width Modulator for Motor Control (PWMMC) supports six independent PWM outputs or three complementary pairs with configurable dead-time, top/bottom correction via motor phase current polarity sensing, and hardware fault shutdown triggered by PTD[3:0] inputs - enabling safe, responsive BLDC and stepper motor commutation without software intervention.

Key Specifications

Pinout & Package

MC68HC908MR32CB is housed in a 48-pin LQFP package (7 mm × 7 mm, 0.5 mm pitch) with exposed thermal pad. Pin functions are defined per Freescale Document MC68HC908MR32 Rev. 6.1, Section 1.4 "Pin Assignments".

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9S08MM128CLD and S9KEAZN64AMLH, the MC68HC908MR32CB offers optimized cost and footprint for standalone, single-motor applications where CAN or floating-point computation is unnecessary - delivering deterministic real-time response with minimal BOM count.

Availability

MC68HC908MR32CB is available at Aetrix Electronics and suitable for industrial motor drives, automotive accessory modules, and HVAC blower control systems requiring stable component supply, long-term lifecycle support, and automotive-grade qualification.

Supply support for MC68HC908MR32CB 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

NXP Semiconductors is a global semiconductor leader focused on secure connectivity solutions for automotive, industrial, and IoT applications.

The MC68HC908MR32CB belongs to the legacy HCS08 microcontroller family, designed specifically for cost-sensitive, high-reliability motor control applications where deterministic timing, hardware fault response, and analog integration are essential.

FAQ

What is the maximum operating frequency of the MC68HC908MR32CB?

The MC68HC908MR32CB supports a maximum bus frequency of 8 MHz, achieved via its integrated PLL clock generator. This frequency is sustained across the full operating voltage range (2.7–5.5 V) and ambient temperature range (–40°C to +105°C), enabling consistent PWM resolution and ADC sampling rates in demanding motor control environments. The PLL allows stable high-speed operation even when using low-cost, low-frequency crystals.

Does the MC68HC908MR32CB support in-application programming (IAP) of its FLASH memory?

Yes, the MC68HC908MR32CB supports in-application programming of its 32 KB FLASH memory using the standard Freescale FLASH command sequence. This capability enables field firmware updates, parameter storage, and bootloader implementation without external programming hardware. The FLBPR register provides hardware block protection to prevent accidental erasure of critical code sections during runtime operations.

How does the hardware fault protection work on the MC68HC908MR32CB?

The MC68HC908MR32CB uses dedicated PTD[3:0] pins (FAULT1–FAULT4) as asynchronous hardware fault inputs. When any of these pins transitions low, all six PWM outputs are disabled within ≤2 µs - faster than any software interrupt response. The fault condition latches until cleared by software, ensuring no spurious re-enabling. This mechanism is essential for meeting IEC 61800-5-2 functional safety requirements in motor drives.

Can the MC68HC908MR32CB operate from a 3.3 V supply?

Yes, the MC68HC908MR32CB operates across a 2.7 V to 5.5 V supply range, making it fully compatible with 3.3 V systems. Its I/O pins are 5 V tolerant when configured as inputs, and its internal voltage regulators ensure stable analog reference (VREFH/VREFL) and PLL operation at 3.3 V - eliminating level-shifting components in mixed-voltage designs involving sensors or communication interfaces.

What development tools are supported for the MC68HC908MR32CB?

The MC68HC908MR32CB is supported by the CodeWarrior Development Studio for HCS08 (legacy), P&E Micro's Multilink debug probes, and open-source GCC-based toolchains with HCS08 backend. Freescale-provided BDM (Background Debug Mode) interface enables full-speed debugging, flash programming, and real-time register inspection - critical for validating motor control timing and fault response behavior.