NXP Semiconductors MC68HC908GT16CFB

Overview

MC68HC908GT16CFB from NXP Semiconductors (formerly Freescale) is an 8-bit HCS08-core microcontroller with 16 KB on-chip Flash, 512 B RAM, and integrated peripherals including 8-channel 10-bit ADC, ESCI, SPI, TIM, KBI, and COP watchdog. It operates at up to 8 MHz bus frequency, supports 2.7–5.5 V supply, and targets low-cost embedded control in industrial sensors and appliance subsystems.

For engineers reviewing the MC68HC908GT16CFB datasheet, MC68HC908GT16CFB pinout, MC68HC908GT16CFB application, or MC68HC908GT16CFB equivalent, key selection criteria include Flash endurance (10k erase/write cycles), internal clock generator trim capability, 5 V-tolerant I/O on Port A/B/C, and monitor-mode debug support via dedicated RST/IRQ pins.

Technical Context

The MC68HC908GT16CFB implements the CPU08 core with 16-bit address space, indexed addressing, and 72-instruction set optimized for compact code. Its System Integration Module (SIM) integrates reset control, clock generation, and interrupt arbitration with configurable COP timeout (1.0–4.1 ms) and low-voltage inhibit (LVI) threshold at 2.5 V nominal.

Peripherals are memory-mapped and share a unified I/O register space: ADC uses VREFH/VREFL references for 10-bit conversions in 25 µs typical; ESCI supports asynchronous serial communication at up to 115.2 kbps with programmable prescaler; SPI operates in master/slave mode with 4-wire interface and independent clock polarity/phase control.

Key Specifications

Pinout & Package

MC68HC908GT16CFB is housed in a 48-pin QFP (Quad Flat Package) with 0.5 mm pitch, JEDEC MS-026AC compliant, and thermal pad exposed on underside for enhanced heat dissipation in high-duty-cycle applications.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9RS08KA8CFD, MC68HC908GT16CFB delivers superior peripheral integration and Flash endurance; versus S9KEAZ128AMLH, it offers lower power in simple deterministic control loops but lacks CAN and modern development tooling.

Availability

MC68HC908GT16CFB is available at Aetrix Electronics and suitable for industrial sensor nodes, home appliance control units, and automotive body electronics requiring stable component supply across long-lifecycle production programs.

Supply support for MC68HC908GT16CFB 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 delivering secure, connected, and intelligent solutions for automotive, industrial, IoT, and mobile applications.

The MC68HC908GT16CFB belongs to the legacy HCS08 microcontroller family, designed for cost-sensitive, low-power embedded control where deterministic real-time response and field-programmable Flash are essential.

FAQ

What is the maximum operating frequency of the MC68HC908GT16CFB?

The MC68HC908GT16CFB supports a maximum bus frequency of 8 MHz, achieved using its internal digitally controlled oscillator (DCO) or external crystal source. This frequency defines instruction execution speed and peripheral timing - for example, ESCI baud rates scale directly with bus clock, and ADC conversion time remains fixed at ~25 µs regardless of bus speed due to internal timing circuitry. The DCO's ±4% accuracy is sufficient for most non-precision timing applications.

Does the MC68HC908GT16CFB support in-circuit programming without a dedicated debugger?

Yes, the MC68HC908GT16CFB supports in-circuit programming via its on-chip serial monitor mode, activated by asserting RST and IRQ simultaneously during power-up. This requires only two pins and a simple level-shifter interface - no JTAG or BDM hardware is needed. The monitor firmware allows reading/writing Flash and RAM, verifying checksums, and executing code from RAM, making MC68HC908GT16CFB suitable for field firmware updates and low-cost production programming.

How does the COP watchdog function in the MC68HC908GT16CFB?

The Computer Operating Properly (COP) module in the MC68HC908GT16CFB is a windowed watchdog timer with four selectable timeout periods (1.0, 2.1, 3.1, or 4.1 ms). It must be cleared within each window by writing to the COPCTL register; failure triggers a hardware reset. During debug break mode, COP is automatically disabled to prevent spurious resets, and it remains inactive until re-enabled by software after reset. This behavior ensures safe development while maintaining robust runtime supervision in deployed MC68HC908GT16CFB systems.

Can the ADC on the MC68HC908GT16CFB operate independently of the main CPU clock?

No - the ADC in the MC68HC908GT16CFB derives its conversion clock from the bus clock via a programmable prescaler (ADCLK), meaning its timing is synchronized to the CPU's operating frequency. However, ADC operation is autonomous once triggered: conversions proceed without CPU intervention, and completion generates an interrupt or sets a flag in the ADCSC register. This allows the CPU to enter Wait mode during acquisition, reducing power consumption while maintaining precise sampling intervals tied to the system clock.

What packaging and RoHS compliance status applies to the MC68HC908GT16CFB?

The MC68HC908GT16CFB is supplied in a 48-pin QFP package (JEDEC MS-026AC) with lead-free (Pb-free) terminations and complies with EU RoHS Directive 2011/65/EU. The package features an exposed thermal pad on the underside for improved thermal performance in thermally constrained PCB layouts. NXP confirms full RoHS compliance for this part number, with no exemptions applied - all homogeneous materials meet the 0.1 wt% threshold for restricted substances including lead, mercury, cadmium, hexavalent chromium, PBB, and PBDE.