NXP Semiconductors MC908GT8CBE

Overview

MC908GT8CBE from Freescale Semiconductor is an 8-bit HCS08-core microcontroller with 8 KB on-chip flash memory, 512 bytes RAM, and integrated peripherals including 8-channel 10-bit ADC, SPI, ESCI (UART), and KBI. 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 motor interfaces.

For engineers reviewing the MC908GT8CBE datasheet, MC908GT8CBE pinout, MC908GT8CBE application, or MC908GT8CBE equivalent, key selection considerations include its 40-pin PDIP package, internal clock generator with DCO trim capability, COP watchdog timeout configurability, and compatibility with legacy HC08 development tools and debug monitors.

Technical Context

The MC908GT8CBE implements the CPU08 core with 16-bit address space, indexed addressing modes, and 72-instruction set optimized for compact code density. Its System Integration Module (SIM) integrates reset control, clock generation, COP watchdog, and interrupt vector management - all configurable via dedicated registers without external logic.

Peripheral integration includes a 10-bit successive-approximation ADC with programmable conversion time (16–256 µs), ESCI supporting asynchronous full-duplex UART operation at up to 115.2 kbps, and SPI master/slave mode with independent baud rate control. All I/O ports support configurable pull-ups and digital input filtering.

Key Specifications

Pinout & Package

MC908GT8CBE is housed in a 40-pin plastic dual in-line package (PDIP) with 0.6-inch body width and 0.1-inch lead pitch. Pin assignments follow standard HC08 GT-series layout with dedicated VDD/VSS pairs, oscillator inputs (PTE4/OSC1, PTE3/OSC2), reset (RST), IRQ, and five I/O ports (A–E).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC908GT16CBE, the MC908GT8CBE offers identical peripheral functionality at lower memory cost; versus MC9RS08KA8CP, it provides greater I/O flexibility and legacy toolchain compatibility at the expense of modern debug features and package size.

Availability

MC908GT8CBE is available at Aetrix Electronics and suitable for industrial sensor nodes, home appliance control systems, and legacy equipment retrofits requiring stable component supply and long-term obsolescence management.

Supply support for MC908GT8CBE 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) pioneered 8-bit microcontroller architectures for industrial and automotive applications, emphasizing robustness, low power, and toolchain longevity.

The MC908GT8CBE belongs to the HC08 family designed for cost-sensitive, real-time embedded control - balancing performance, peripheral integration, and ease of migration from earlier HC05/HC11 platforms.

FAQ

What is the maximum operating frequency of the MC908GT8CBE?

The MC908GT8CBE achieves a maximum bus frequency of 8 MHz when powered at 4.5–5.5 V. At lower supply voltages (2.7–4.5 V), the maximum rated bus frequency is 4 MHz per the device's DC electrical characteristics table. This limitation ensures timing margin for internal flash access and peripheral synchronization under reduced voltage conditions. The MC908GT8CBE uses an internal digitally controlled oscillator (DCO) whose frequency is trimmed and scaled via the ICG module registers.

Does the MC908GT8CBE support in-circuit debugging?

Yes, the MC908GT8CBE supports in-circuit debugging via its background debug mode (BDM) interface using a single-wire connection (BKGD pin). This allows full read/write memory access, register inspection, breakpoint setting, and real-time execution control without halting the target system. Debugging requires a compatible BDM pod or debugger such as the P&E Micro USB-ML-12 or Freescale DEMO908GT8 evaluation board. The MC908GT8CBE does not require external debug hardware beyond the BKGD pull-up resistor and connector.

Can the MC908GT8CBE operate from a 3.3 V supply?

Yes, the MC908GT8CBE is fully specified to operate across 2.7–5.5 V, making 3.3 V a valid and commonly used supply voltage. At 3.3 V, the maximum bus frequency is 4 MHz, and all I/O pins remain 5 V tolerant when configured as inputs. The ADC reference can be tied to 3.3 V for ratiometric measurements, and the internal voltage regulator for the analog section (VDDA) is internally decoupled to ensure stable operation. No external level shifters are needed for interfacing with 3.3 V peripherals.

How is the ADC calibrated on the MC908GT8CBE?

The MC908GT8CBE does not include factory-trimmed ADC calibration constants. Calibration is performed in-system by the application firmware using the built-in self-test mode: shorting VREFL to VSS and VREFH to VDD, then performing conversions at known reference points to compute offset and gain correction factors. The ADC Status and Control Register (ADSC) provides COCO (conversion complete) flag and channel select bits, while the ADC Data Register (ADDATA) holds the 10-bit result. Users implement linear correction in software using two-point calibration.

Is the MC908GT8CBE pin-compatible with the MC68HC908GT8?

Yes, the MC908GT8CBE is a direct replacement for the MC68HC908GT8 - sharing identical pinout, electrical specifications, memory map, and register definitions. The "MC908" prefix denotes the later Freescale branding update; the underlying silicon and mask set are functionally identical. Firmware, PCB layout, and toolchain configurations developed for MC68HC908GT8 require no modification to operate with MC908GT8CBE, including BDM debug sessions and flash programming algorithms.