NXP Semiconductors MC68HC908SR12CFA

Overview

MC68HC908SR12CFA from NXP (formerly Freescale) is an 8-bit HCS08-core microcontroller with 12 KB on-chip FLASH, 512 B RAM, integrated 10-bit ADC (8 channels), dual SCI, I²C-compatible MMIIC, PWM, TIM, and TBM modules. It operates from 2.7–5.5 V and supports crystal, RC, or internal oscillator sources - used in industrial sensor nodes and motor control subsystems.

For engineers reviewing the MC68HC908SR12CFA datasheet, MC68HC908SR12CFA pinout, MC68HC908SR12CFA application, or MC68HC908SR12CFA equivalent, key selection criteria include its 44-pin LQFP package, PLL-based clock generation up to 8 MHz bus speed, on-chip COP watchdog, low-voltage inhibit (LVI), and monitor ROM for in-system programming.

Technical Context

The MC68HC908SR12CFA implements the HCS08 CPU core with 16-bit address space, supporting indexed, extended, and relative addressing modes. Its Clock Generator Module (CGM) integrates a PLL with programmable multipliers (×1 to ×32) and reference dividers, enabling precise bus frequency synthesis from low-frequency crystals (e.g., 32.768 kHz).

System integration includes a System Integration Module (SIM) managing reset sources (POR, LVI, COP, illegal opcode), interrupt prioritization across 16 vectors, and power management with Wait/Stop modes. The Analog Module provides temperature sensing, current flow detection, and amplifier gain control independent of ADC operation.

Key Specifications

Pinout & Package

MC68HC908SR12CFA is housed in a 44-pin LQFP (7 mm × 7 mm, 0.8 mm pitch) package with exposed thermal pad. Pin functions are defined per Section 1.5 (Pin Assignments) and Section 1.6 (Pin Functions) of the Rev. 5.0 datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9RS08KA8CFD and S9KEAZ128AMLH, the MC68HC908SR12CFA offers balanced legacy compatibility, integrated PLL-based timing, and I²C support without ARM migration overhead - ideal for incremental upgrades of existing HCS08-based designs.

Availability

MC68HC908SR12CFA is available at Aetrix Electronics and suitable for industrial sensor nodes, BLDC motor controllers, smart power outlets, and medical infusion pump controllers requiring stable component supply and long-term manufacturing continuity.

Supply support for MC68HC908SR12CFA 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 MC68HC908SR12CFA belongs to the HCS08 microcontroller family, designed for cost-sensitive, low-power embedded control applications requiring robust analog integration, deterministic real-time response, and field-programmable FLASH.

FAQ

What is the maximum operating frequency of the MC68HC908SR12CFA bus clock?

The MC68HC908SR12CFA achieves a maximum bus clock frequency of 8 MHz using its integrated PLL. This is attained by configuring the PLL multiplier and reference divider to synthesize 8 MHz from a 32.768 kHz crystal or other supported oscillator source. The PLL allows stable high-speed operation even with low-frequency, low-cost crystals - a key advantage over fixed-frequency oscillator-only MCUs. Bus speed directly determines instruction throughput and peripheral timing resolution.

Does the MC68HC908SR12CFA support in-system programming without external hardware?

Yes, the MC68HC908SR12CFA includes a 2 KB Monitor ROM (MON) that enables in-system programming via its SCI interface. Using standard UART signals (TxD/RxD), users can reprogram the 12 KB FLASH memory, read/write RAM, and verify code integrity without a dedicated programmer. This feature is documented in Section 10 of the Rev. 5.0 datasheet and eliminates the need for external debug probes during field updates or production programming - significantly reducing tooling costs for the MC68HC908SR12CFA.

How many analog input channels does the ADC in the MC68HC908SR12CFA support?

The MC68HC908SR12CFA features a 10-bit successive-approximation ADC with eight analog input channels (ATD0–ATD7), mapped to PTC0–PTC3 and additional dedicated pins. These channels support single-ended or differential acquisition, auto-scan sequencing, and result justification (left/right-aligned). The ADC operates across the full 2.7–5.5 V supply range and includes dedicated VREFH/VREFL pins for precision reference control - critical for accurate sensor interfacing in the MC68HC908SR12CFA.

What safety features are built into the MC68HC908SR12CFA for reliable operation?

The MC68HC908SR12CFA integrates multiple hardware safety mechanisms: a windowed Computer Operating Properly (COP) watchdog with software-disable option, Low-Voltage Inhibit (LVI) circuitry that resets the device below 2.5 V to prevent FLASH corruption, and illegal opcode/address detection that triggers controlled reset. These features operate independently of firmware execution and are active in all power modes - ensuring fail-safe behavior in mission-critical applications using the MC68HC908SR12CFA.

Can the MC68HC908SR12CFA drive I²C peripherals directly?

Yes, the MC68HC908SR12CFA includes a Multi-Master IIC Interface (MMIIC) module compliant with Philips I²C Specification v2.1. Pins PTB0/SDA0 and PTB1/SCL0 provide open-drain I²C signals with internal pull-ups, supporting standard-mode (100 kbps) and fast-mode (400 kbps) transfers. The MMIIC handles arbitration, clock stretching, and ACK/NACK generation in hardware - enabling robust, multi-master communication with sensors, EEPROMs, and other I²C devices without bit-banging overhead in the MC68HC908SR12CFA.