NXP Semiconductors MC68HC908MR32CFU

Overview

MC68HC908MR32CFU from Freescale Semiconductor is an 8-bit HCS08-core microcontroller with 32 KB on-chip FLASH, 1.5 KB RAM, and integrated motor-control PWM (PWMMC), 10-bit ADC (8+2 channels), SCI/SPI/SCI interfaces, and PLL-based clock generation. It operates at up to 8 MHz bus frequency and targets embedded motor control, industrial sensing, and appliance systems requiring real-time I/O and deterministic timing.

For engineers reviewing the MC68HC908MR32CFU datasheet, MC68HC908MR32CFU pinout, MC68HC908MR32CFU application, or MC68HC908MR32CFU equivalent, key selection criteria include its 48-pin LQFP package, dedicated fault-input pins (PTD0–PTD3), complementary PWM output capability with dead-time insertion, and monitor-mode debug support via IRQ pin entry.

Technical Context

The MC68HC908MR32CFU implements the HCS08 CPU core with 8-level hardware stack, supports wait/stop low-power modes, and integrates a Phase-Locked Loop (PLL) for precise bus clock synthesis from external crystal or RC source. Its PWMMC module provides six independent or three complementary PWM outputs with programmable dead time and top/bottom correction driven by motor phase current polarity sensing.

The device includes a 10-bit successive-approximation ADC with eight analog inputs (ATD0–ATD7) plus two auxiliary inputs (ATD8/ATD9), configurable sample-and-hold, and conversion times as low as 7 µs per channel. Memory protection is enforced via FLASH Block Protect Register (FLBPR) at $FF7E and CONFIG register lock bits.

Key Specifications

Pinout & Package

The MC68HC908MR32CFU is housed in a 48-pin LQFP (7 mm × 7 mm) package with exposed thermal pad, rated for –40°C to +85°C industrial temperature operation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC908MR16CFU, the MC68HC908MR32CFU offers double FLASH capacity for complex control algorithms and larger lookup tables; versus S9KEAZ128AMLH, it delivers lower-cost, proven 8-bit determinism but lacks ARM ecosystem features like CMSIS-DSP or RTOS support.

Availability

MC68HC908MR32CFU is available at Aetrix Electronics and suitable for industrial motor control, appliance mainboards, and sensor-edge devices requiring stable component supply across long production lifecycles.

Supply support for MC68HC908MR32CFU 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, analog, and connectivity solutions for automotive, industrial, and consumer markets.

The MC68HC908MR32CFU belongs to the HCS08 microcontroller family, engineered specifically for cost-sensitive, real-time motor control and industrial automation applications requiring robust analog integration and deterministic PWM timing.

FAQ

What is the maximum bus frequency supported by the MC68HC908MR32CFU?

The MC68HC908MR32CFU supports a maximum bus frequency of 8 MHz, achieved using its integrated Phase-Locked Loop (PLL) to multiply a lower-frequency crystal input (e.g., 32.768 kHz or 4 MHz). This frequency governs instruction execution speed, peripheral timing, and ADC conversion rate. The PLL configuration is controlled via CGM registers including PLLCR, PLLBCR, and PLLPR, and must be initialized during startup sequence in the MC68HC908MR32CFU firmware.

Does the MC68HC908MR32CFU support in-system programming without external hardware?

Yes, the MC68HC908MR32CFU includes 256 bytes of on-chip monitor ROM that enables in-system programming (ISP) of its 32 KB FLASH memory. Entry is triggered by holding the IRQ pin low for at least 16 consecutive bus cycles after reset. Once active, the monitor ROM provides a serial bootloader interface via the SCI module, allowing firmware updates using only a UART connection - no external programmer is required for field upgrades of the MC68HC908MR32CFU.

How many fault inputs does the MC68HC908MR32CFU provide for motor control safety?

The MC68HC908MR32CFU provides four dedicated fault inputs - PTD0/FAULT1, PTD1/FAULT2, PTD2/FAULT3, and PTD3/FAULT4 - each capable of asynchronously disabling all PWM outputs within one bus cycle upon assertion. These inputs are electrically isolated from the main I/O logic and directly tied to the PWMMC module, ensuring fail-safe response to overcurrent, overtemperature, or short-circuit conditions without CPU involvement. This hardwired safety path is a defining feature of the MC68HC908MR32CFU in motor drive applications.

Can the MC68HC908MR32CFU operate from a 3.3 V supply?

Yes, the MC68HC908MR32CFU operates across a supply voltage range of 2.7 V to 5.5 V, making it fully compatible with 3.3 V systems. At 3.3 V, the maximum bus frequency is reduced to approximately 5.5 MHz due to internal timing constraints, but all peripherals - including ADC, PWM, SCI, and SPI - remain functional. I/O pins are 5 V tolerant when configured as inputs, simplifying level-shifting requirements in mixed-voltage designs using the MC68HC908MR32CFU.

What ADC configuration options are available on the MC68HC908MR32CFU?

The MC68HC908MR32CFU features a 10-bit successive-approximation ADC with 10 input channels (ATD0–ATD9), selectable sample-and-hold time, left/right result justification, and continuous or single-conversion modes. Conversion time is programmable down to 7 µs per channel using the ADCClk register. Inputs are multiplexed across Port B (ATD0–ATD7) and Port C (ATD8–ATD9), and the ADC supports internal reference (VREFH/VREFL) or external reference configurations - all managed via ADC Status and Control Register (ADSCR) and ADC Clock Register (ADCClk) in the MC68HC908MR32CFU memory map.