NXP Semiconductors MCF51EM256CLK

Overview

MCF51EM256CLK from NXP Semiconductors (formerly Freescale) is a 32-bit ColdFire V1 RISC microcontroller in an 80-pin LQFP package, operating up to 50.33 MHz at 2.5–3.6 V and 20 MHz at 1.8–3.6 V, featuring 256 KB flash, 16 KB RAM, ultra-low-power IRTC with calendar, and integrated 16-bit SAR ADC - deployed in battery-powered industrial HMI and portable medical instrumentation.

For engineers reviewing the MCF51EM256CLK datasheet, MCF51EM256CLK pinout, MCF51EM256CLK application, or MCF51EM256CLK equivalent, this page delivers verified functional identity, validated 80-pin LQFP terminal mapping, confirmed low-power run/stop mode behavior, and real-world substitution guidance for legacy ColdFire-based designs requiring long-term supply continuity.

Technical Context

The MCF51EM256CLK implements the ColdFire V1 core (ISA_C + MAC), executing 32-bit instructions with hardware-accelerated 16×16±32 multiply-accumulate operations. Its system integration unit (SIM) manages clock routing from dual independent oscillators (XOSC1 for IRTC, XOSC2 for CPU/peripherals) and the internal clock source (ICS) with FLL-based frequency multiplication.

Peripherals include three SCIs supporting RS-232/LIN, three SPIs (SPI1 with 32-bit FIFO, SPI2/SPI3 with open-drain options), I²C up to 100 kbps, two analog comparators (PRACMP1/PRACMP2) with interrupt edge select, and a programmable delay block (PDB) synchronized to four ADC16 modules for deterministic sampling sequences.

Key Specifications

Pinout & Package

80-pin LQFP (14 mm × 14 mm), RoHS-compliant, thermal pad exposed on underside per Freescale mechanical drawing 917A-03.

Key Features

Applications

Equivalent & Alternatives

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

Compared with Kinetis KL27Z128VLH4, MCF51EM256CLK delivers integrated LCD/IRTC functionality and ColdFire ISA continuity; versus MCF51JM128CLK, it provides double flash capacity and four additional ADC inputs - critical for feature-rich HMI or multi-sensor monitoring.

Availability

MCF51EM256CLK is available at Aetrix Electronics and suitable for industrial HMI, portable medical instrumentation, smart energy metering, and automotive body control applications requiring stable component supply and long-term lifecycle support.

Supply support for MCF51EM256CLK 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 acquired Freescale in 2015 and maintains legacy ColdFire product support, focusing on industrial, automotive, and IoT applications with emphasis on reliability and long-term availability.

The MCF51EM256CLK belongs to the ColdFire EM series - designed specifically for ultra-low-power, highly integrated embedded control in resource-constrained environments where LCD drive, precision ADC, and battery-backed RTC are essential.

FAQ

What is the maximum operating frequency of the MCF51EM256CLK and under what voltage conditions?

The MCF51EM256CLK achieves a maximum core frequency of 50.33 MHz when supplied between 2.5 V and 3.6 V across the –40 °C to +85 °C temperature range. At lower voltages (1.8 V to 3.6 V), the maximum guaranteed frequency is 20 MHz. These values are specified in Section 1.3.1 of the Rev.3 datasheet and reflect actual silicon characterization, not theoretical limits.

Does the MCF51EM256CLK support true pin-to-pin compatibility with other members of the MCF51EM series?

The MCF51EM256CLK uses the 80-pin LQFP package (917A-03), which shares identical pinout and footprint with the MCF51EM128CLK. However, it is not pin-compatible with 100-pin variants like MCF51EM256CLL due to missing signals (e.g., AD4, DADP0–DADM3, LCD16–LCD20). Software must account for reduced PRACMP1 inputs (3 vs. 5) and fewer ADC channels in the 80-pin configuration.

How does the Programmable Delay Block (PDB) function in the MCF51EM256CLK?

The PDB in the MCF51EM256CLK is a dedicated 16-bit timer with modulus and prescaler that generates eight synchronized trigger outputs - two per ADC16 module - to coordinate precise, repeatable sampling sequences. It operates independently of CPU load and supports programmable sequence completion interrupts, enabling deterministic analog acquisition in real-time control loops without software intervention.

Can the MCF51EM256CLK operate its LCD driver and ADC simultaneously on shared pins?

Yes - pins such as PTF0–PTF7 serve dual roles as LCD front-plane outputs and ADC inputs (AD16–AD19). The LCD module and ADC are electrically isolated within the chip; proper sequencing (e.g., disabling LCD charge pump during ADC conversion) ensures accurate 16-bit measurements. This capability is documented in Sections 1.3.1 and 2.11 of the datasheet.

What debug interface does the MCF51EM256CLK provide, and is it compatible with standard tools?

The MCF51EM256CLK integrates a ColdFire DEBUG_Rev_B+ interface accessible via the BKGD/MS pin, supporting single-wire BDM (Background Debug Mode) with electrical compatibility to S08-family debug modules. It works with standard P&E Micro and SEGGER J-Link BDM adapters and supports six hardware breakpoints, real-time trace buffer, and on-chip flash programming - all verified in Freescale Application Note AN3782.