NXP Semiconductors MC68HC908LJ24CFU

Overview

MC68HC908LJ24CFU from Freescale Semiconductor is an 8-bit HCS08-core microcontroller with 24 KB on-chip FLASH, 512 B RAM, integrated LCD driver (up to 32 segments), real-time clock (RTC), IRSCI, SPI, I²C, and 10-bit ADC. It operates at up to 8 MHz bus frequency and supports low-power stop/wait modes for battery-powered instrumentation and control panels.

For engineers reviewing the MC68HC908LJ24CFU datasheet, MC68HC908LJ24CFU pinout, MC68HC908LJ24CFU application, or MC68HC908LJ24CFU equivalent, key selection criteria include its integrated RTC accuracy (±1 ppm calibration), 32-segment LCD drive capability without external bias circuitry, and IRSCI module supporting NEC and RC-5 infrared protocols in embedded human-interface applications.

Technical Context

The MC68HC908LJ24CFU implements the HCS08 CPU core with enhanced addressing modes and a 16-bit index register. Its Clock Generator Module (CGM) integrates a PLL with programmable multipliers (×1 to ×32) and reference dividers, enabling precise bus clock synthesis from internal RC or external crystal sources.

The System Integration Module (SIM) coordinates reset sources-including POR, LVI, COP timeout, and external RST-and manages low-power transitions. The Real Time Clock (RTC) includes calendar, alarm, chronograph, and temperature-compensated calibration registers accessible via dedicated memory-mapped addresses.

Key Specifications

Pinout & Package

MC68HC908LJ24CFU is housed in a 64-pin QFP (Quad Flat Package) with 0.5 mm pitch, thermally enhanced for industrial ambient operation up to +85°C. Pin functions 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 MC68HC908LJ24CFU, the MC68HC908LK24CFU retains full LCD/RTC/ADC capability but trades IRSCI for KBI-making it optimal for keypad-centric designs-while the MC9RS08LA8CFU abandons both RTC and IRSCI to integrate USB, requiring architectural redesign for timekeeping and remote control functions.

Availability

MC68HC908LJ24CFU is available at Aetrix Electronics and suitable for industrial control panels, portable medical instruments, smart energy meters, and appliance remote hubs requiring stable component supply across extended product lifecycles.

Supply support for MC68HC908LJ24CFU 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) designed high-integration, low-power microcontrollers for cost-sensitive industrial and consumer applications requiring mixed-signal peripherals and long-term supply stability.

The MC68HC908LJ24CFU belongs to the HCS08 family, engineered specifically for human-interface applications demanding integrated LCD drive, precise RTC, and infrared communication-all within a single die and standard QFP package.

FAQ

What is the maximum operating frequency of the MC68HC908LJ24CFU bus clock?

The MC68HC908LJ24CFU supports a maximum bus clock frequency of 8 MHz, achieved via its integrated Clock Generator Module (CGM) PLL using an external 1–8 MHz crystal or internal RC oscillator. This frequency is confirmed in Section 8.4.2 (PLL Circuits) and Table 24-1 (DC Electrical Characteristics) of the Rev. 2.1 datasheet, and applies directly to the MC68HC908LJ24CFU variant.

Does the MC68HC908LJ24CFU support in-system programming of its FLASH memory?

Yes, the MC68HC908LJ24CFU supports in-system programming (ISP) of its 24 KB FLASH memory using the on-chip Monitor ROM (MON) accessed via the IRSCI or SCI interface. The datasheet confirms ISP capability in Section 4.7 (FLASH Program Operation) and Section 10.4.5 (Commands), with PRGRNGE and ERARNGE routines resident in MON ROM for field updates without external programmers.

How many LCD segments can the MC68HC908LJ24CFU drive, and does it require external bias components?

The MC68HC908LJ24CFU drives up to 32 LCD segments using its integrated 3-backplane, 32-frontplane multiplexed driver. It generates VLCD internally (Section 1.6.3) and requires no external bias resistors or capacitors-confirmed in Section 17.3 (Functional Description) and Figure 17-1 (LCD Block Diagram) of the datasheet.

What infrared protocols are natively supported by the IRSCI module in the MC68HC908LJ24CFU?

The IRSCI module in the MC68HC908LJ24CFU natively supports NEC and RC-5 infrared protocols, with hardware-assisted encoding and decoding. Section 13.6 (Infrared Functional Description) and Section 13.11.8 (SCI Infrared Control Register) specify register-controlled carrier frequency (30–56 kHz), modulation depth, and frame format handling for both protocols.

Is the RTC in the MC68HC908LJ24CFU temperature-compensated, and how is calibration performed?

The MC68HC908LJ24CFU RTC includes temperature-compensated calibration via the RTCCOMR and RTCCDAT registers (Section 12.7), allowing software adjustment of oscillator drift in ±1 ppm increments. Calibration is performed by writing correction values to RTCCDAT after measuring deviation against a reference clock, as detailed in Section 12.7.1 (Calibration Error).