NXP Semiconductors MCF51EM256CLLR

Overview

MCF51EM256CLLR from NXP Semiconductors (formerly Freescale) is a 32-bit ColdFire V1 RISC microcontroller designed for ultra-low-power embedded applications requiring integrated analog, timing, and LCD control. It features 256 KB flash, 16 KB RAM, 50.33 MHz CPU operation at 3.6–2.5 V, <1.3 μA battery-mode current, and an independent RTC with calendar and tamper detection - deployed in portable medical monitors and industrial handheld terminals.

For engineers reviewing the MCF51EM256CLLR datasheet, MCF51EM256CLLR pinout, MCF51EM256CLLR application, or MCF51EM256CLLR equivalent, key selection criteria include its dual crystal oscillator architecture (XOSC1 for IRTC, XOSC2 for CPU), 4-channel 16-bit ADC with stop3-mode operation, programmable delay block (PDB) for synchronized sampling, and 100-pin LQFP package with 47 GPIOs including rapid GPIO support.

Technical Context

The MCF51EM256CLLR implements the ColdFire V1 core (ISA_C + MAC) with hardware multiply-accumulate optimized for 16×16±32 operations. Its system integration unit (SIM) manages clock distribution across three independent domains: CPU/peripherals (driven by ICS with FLL), IRTC (powered by XOSC1), and LCD (with internal charge pump).

It integrates four ADC16 modules (16-bit resolution, 24 single-ended/4 differential inputs), two PRACMP analog comparators with interrupt edge select and internal reference options, and a PDB with 8 trigger outputs - enabling deterministic, low-jitter coordination of ADC conversions without CPU intervention.

Key Specifications

Pinout & Package

100-pin LQFP (14 mm × 14 mm), RoHS-compliant, moisture sensitivity level 3. Pin functions are multiplexed per Table 4 of Rev.3 datasheet; LCD pins default to open-drain unless configured via FCDEN/VSUPPLY/RVEN bits.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MCF51EM256CLLR, KL27Z128VLH4 offers ARM toolchain familiarity but sacrifices integrated LCD, IRTC autonomy, and PDB-based ADC synchronization; MCF51JM128CLK preserves full ColdFire peripheral compatibility but constrains memory and I/O scalability.

Availability

MCF51EM256CLLR is available at Aetrix Electronics and suitable for portable medical monitors, industrial handheld terminals, smart utility meters, and low-power home automation hubs requiring stable component supply, long-term lifecycle support, and qualified automotive-grade alternatives.

Supply support for MCF51EM256CLLR 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 continues to support ColdFire legacy products through its Industrial & IoT portfolio, emphasizing reliability, long-term availability, and functional safety readiness.

The MCF51EM256CLLR belongs to the ColdFire EM series - designed specifically for ultra-low-power, highly integrated embedded control in battery-operated instrumentation, metering, and human-interface devices with on-chip LCD, RTC, and analog subsystems.

FAQ

What is the maximum operating frequency of the MCF51EM256CLLR and under what voltage conditions?

The MCF51EM256CLLR operates at up to 50.33 MHz when supplied between 3.6 V and 2.5 V across the –40 °C to +85 °C temperature range. At lower voltages (3.6 V to 1.8 V), the maximum guaranteed frequency is 20 MHz. These specifications are defined in Section 1.3.1 of the Rev.3 datasheet and validated across process corners and temperature extremes. The MCF51EM256CLLR uses an internal clock source (ICS) with frequency-locked-loop (FLL) to derive these frequencies from external crystals or internal references.

Does the MCF51EM256CLLR support true hardware debugging during low-power operation?

Yes, the MCF51EM256CLLR supports real-time debugging via its integrated Background Debug Module (BDM) using the BKGD/MS pin. It maintains debug visibility in all run, wait, and stop modes except stop3 - where debug access is disabled to preserve ultra-low current. The MCF51EM256CLLR implements ColdFire DEBUG_Rev_B+ with six hardware breakpoints (four PC, one address, one data) and an on-chip trace buffer, enabling non-intrusive analysis of power-state transitions and peripheral behavior without halting execution.

How does the Programmable Delay Block (PDB) interact with the ADC16 modules in the MCF51EM256CLLR?

The PDB in the MCF51EM256CLLR provides eight hardware trigger outputs - two per ADC16 module - to initiate conversions with precise, jitter-free timing. Each PDB channel features a 16-bit counter, modulus register, and 3-bit prescaler, allowing programmable delays and periodic triggering. This eliminates software-based timing loops and enables synchronized multi-ADC sampling for phase-sensitive measurements. The MCF51EM256CLLR's PDB can also generate a sequence completion interrupt upon finishing a defined trigger pattern, streamlining sensor fusion firmware.

Can the MCF51EM256CLLR drive a 4×40 LCD directly without external components?

Yes, the MCF51EM256CLLR integrates a full LCD controller supporting up to 288 segments (8×36) or 160 segments (4×40), including an internal charge pump and programmable contrast control via VREF trimming. When configured with FCDEN=1, VSUPPLY=11, and RVEN=0, LCD pins operate in full-complementary drive mode - eliminating the need for external bias resistors or boost converters. The MCF51EM256CLLR sustains LCD operation in all low-power modes, including stop3, with blink functionality enabled.

What are the key differences between the MCF51EM256CLLR and the MCF51EM256CLK variants?

The MCF51EM256CLLR uses a 100-pin LQFP package (14 mm × 14 mm) with 47 GPIOs, 4× ADC differential inputs, and full peripheral complement including all 100 package-specific signals (e.g., DADP0/DADM0, AD4, LCD16–LCD20). The MCF51EM256CLK uses an 80-pin LQFP (same footprint) with 40 GPIOs and omits 20 pins - reducing ADC differential capability to 2 channels and disabling certain LCD segments and analog inputs. Both share identical core, memory, and electrical specs, but the MCF51EM256CLLR enables higher I/O density and expanded analog interface.