NXP Semiconductors MC68HC908LK24CFU

Overview

MC68HC908LK24CFU from NXP (formerly Freescale) is an 8-bit HCS08 microcontroller with 24 KB on-chip FLASH, 512 B RAM, and integrated LCD driver supporting up to 32 segments. It features a real-time clock (RTC), IRSCI infrared/SCI serial interface, SPI, I²C-compatible MMIIC, 10-bit ADC, and PWM-capable TIM module. Designed for low-power embedded instrumentation and industrial control panels requiring local display and serial telemetry.

For engineers reviewing the MC68HC908LK24CFU datasheet, MC68HC908LK24CFU pinout, MC68HC908LK24CFU application, or MC68HC908LK24CFU equivalent, key selection criteria include its 48-pin QFP package, 3.3–5.5 V operation, SuperFlash® endurance (100k erase/write cycles), RTC calendar/alarm functions, and LCD bias generation capability - all critical for battery-backed metering and human-interface applications.

Technical Context

The MC68HC908LK24CFU implements the HCS08 CPU core with 16-bit address space, supporting wait/stop low-power modes and COP watchdog. Its Clock Generator Module (CGM) integrates a PLL with programmable multipliers (×1 to ×32) and reference dividers for precise bus clock synthesis from internal RC or external crystal sources.

The System Integration Module (SIM) manages reset sources (POR, LVI, COP, illegal opcode), exception handling, and bus timing synchronization. The IRSCI combines infrared modulation/demodulation logic with standard SCI framing, enabling remote control and low-noise serial communication without external transceivers.

Key Specifications

Pinout & Package

MC68HC908LK24CFU is housed in a 48-pin QFP (Quad Flat Package) with 0.5 mm lead pitch, thermally enhanced for industrial ambient operation (–40°C to +85°C). Pin assignments are defined per Section 1.5 (Pin Assignments) and Section 1.6 (Pin Functions) of the Rev. 2.1 datasheet.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC908LK24CFU, the MC9RS08LA8 sacrifices RTC, LCD, and memory for lower cost and smaller footprint, while the MC9S08LG32 extends functionality with CAN and larger memory - making MC68HC908LK24CFU optimal for cost-sensitive, display-centric, time-aware embedded instruments where CAN is unnecessary.

Availability

MC68HC908LK24CFU is available at Aetrix Electronics and suitable for smart metering, industrial HMI, and portable instrumentation requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for MC68HC908LK24CFU 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 MC68HC908LK24CFU belongs to the HCS08 microcontroller family, designed specifically for cost-sensitive, low-power embedded systems requiring integrated human interface (LCD), precise timing (RTC), and robust serial communication (IRSCI, SPI, MMIIC).

FAQ

What is the maximum operating frequency of the MC68HC908LK24CFU?

The MC68HC908LK24CFU supports a maximum bus clock frequency of 20 MHz, achieved using the internal PLL with external crystal or internal RC oscillator. The PLL allows multiplication of reference clocks (e.g., 32.768 kHz or 4 MHz) to generate stable high-speed system clocks while maintaining low-jitter timing for ADC sampling and PWM generation - essential for accurate measurements in the MC68HC908LK24CFU's target applications.

Does the MC68HC908LK24CFU support in-circuit debugging?

Yes, the MC68HC908LK24CFU supports background debug mode (BDM) via the BKGD pin, enabling non-intrusive real-time debugging, flash programming, and memory inspection without halting the CPU. This capability is implemented in the Monitor ROM (MON) and requires only a single-wire BDM interface - simplifying development and field firmware updates for the MC68HC908LK24CFU without additional JTAG hardware.

How does the LCD driver in the MC68HC908LK24CFU differ from basic GPIO-based implementations?

The MC68HC908LK24CFU's LCD driver is a dedicated peripheral with hardware scan timing, VLCD bias generation, and configurable frontplane/backplane mapping - eliminating software-driven bit-banging and external charge pumps. Unlike GPIO-based approaches, it guarantees flicker-free 4-mux operation across all 32 segments, reduces CPU load by >90%, and maintains contrast stability over temperature and supply voltage - a core differentiator for the MC68HC908LK24CFU in display-intensive applications.

Can the MC68HC908LK24CFU operate from a single 3.3 V supply?

Yes, the MC68HC908LK24CFU operates across 3.3 V to 5.5 V, and all I/O pins are 5 V tolerant when VDD ≥ 3.3 V. At 3.3 V, the internal VLCD generator remains functional, and the RTC retains accuracy within specification. This dual-voltage capability allows the MC68HC908LK24CFU to interface directly with both legacy 5 V peripherals and modern 3.3 V sensors without level shifters - simplifying power architecture in mixed-voltage designs.

What is the role of the CGMXFC pin on the MC68HC908LK24CFU?

The CGMXFC pin on the MC68HC908LK24CFU connects to an external capacitor (typically 10–22 nF) that sets the loop filter time constant for the integrated PLL. This capacitor stabilizes PLL lock acquisition, minimizes output jitter, and determines bandwidth response to reference clock variations - directly impacting timing precision for the MC68HC908LK24CFU's bus clock, ADC sampling, and PWM resolution.