NXP Semiconductors MC908QB8VDWE

Overview

MC908QB8VDWE from Freescale Semiconductor is an 8-bit M68HC08 core microcontroller with 8 KB on-chip FLASH memory, 256 B RAM, and integrated peripherals including ADC10 (10-bit, 8-channel), ESCI, SPI, TIM, AWU, COP watchdog, and LVI voltage monitor. It operates at up to 8 MHz bus frequency and supports single-supply operation from 2.7 V to 5.5 V, targeting low-cost embedded control in automotive body electronics and industrial sensors.

For engineers reviewing the MC908QB8VDWE datasheet, MC908QB8VDWE pinout, MC908QB8VDWE application, or MC908QB8VDWE equivalent, this page delivers verified technical context, security-aware FLASH programming behavior, oscillator trimming details, and real-world design constraints for production firmware development and hardware integration.

Technical Context

The MC908QB8VDWE implements the M68HC08 CPU core with 16-bit address space, Harvard architecture instruction fetch, and indexed/stack-relative addressing. Its internal oscillator supports factory-trimmed RC operation at 4.0 MHz ±2% over temperature and voltage, with optional external crystal or ceramic resonator support via OSC1/OSC2 pins.

FLASH memory includes mass erase, page erase, and byte-program capabilities, with security enforced via eight user-defined bytes at $FFF6–$FFFD; monitor mode entry is denied if five or more of those bytes are zero. The ADC10 module provides configurable sample time, programmable clock division, and conversion completion interrupt with 10-bit resolution across eight analog inputs.

Key Specifications

Pinout & Package

MC908QB8VDWE is housed in a 28-pin SOIC (Small Outline Integrated Circuit) package with 300-mil body width and standard 1.27 mm pitch. Pin assignments follow Freescale's MC68HC908QB8 Rev. 3 specification, with dedicated VDD/VSS pairs, oscillator inputs, RESET, IRQ, and peripheral-specific I/O.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 8-bit microcontroller applications.

Compared with MC908QB8VDWE, MC908QY8CDTE offers more RAM but removes ESCI-based LIN support, while S9KEAZ128AMLH delivers modern ARM performance at the cost of complete hardware and software redesign - making MC908QB8VDWE optimal for cost-sensitive, LIN-integrated legacy platforms.

Availability

MC908QB8VDWE is available at Aetrix Electronics and suitable for automotive body control modules, industrial sensor transmitters, home appliance UIs, and medical device interfaces requiring stable component supply, long-term lifecycle support, and qualified manufacturing traceability.

Supply support for MC908QB8VDWE 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 since 2015) pioneered 8-bit MCU architectures for automotive and industrial markets, emphasizing robustness, mixed-signal integration, and production-grade tooling.

The MC68HC08 family - including MC908QB8VDWE - was designed for cost-effective, low-power embedded control where deterministic timing, on-chip FLASH security, and peripheral integration outweigh raw processing speed.

FAQ

What is the maximum bus frequency supported by the MC908QB8VDWE?

The MC908QB8VDWE supports a maximum bus frequency of 8 MHz. This is achieved either by configuring the internal RC oscillator (factory-trimmed to 4.0 MHz ±2%, doubled via BUSCLKX2) or by connecting an external 8 MHz crystal to OSC1/OSC2. The actual achievable frequency depends on supply voltage and temperature, with guaranteed operation across the full 2.7–5.5 V and –40°C to +105°C range per Freescale's MC68HC908QB8 Rev. 3 Electrical Specifications.

How does the FLASH security feature work on the MC908QB8VDWE?

The MC908QB8VDWE implements FLASH security through eight user-programmable bytes stored at memory addresses $FFF6–$FFFD. During monitor mode entry, the host must transmit these exact bytes; if five or more are zero, monitor mode is denied. This prevents unauthorized firmware readout or reprogramming. Users must program all eight locations - even if unused for vectors - to avoid unintentional security bypass, as specified in Freescale's May 2012 Addendum to the MC68HC908QB8 datasheet.

Can the MC908QB8VDWE operate without an external crystal?

Yes, the MC908QB8VDWE can operate without an external crystal. Its internal RC oscillator provides a factory-trimmed 4.0 MHz clock (±2% over voltage and temperature), sufficient for most non-timing-critical applications like keypad scanning, sensor polling, and UART communication at moderate baud rates. External crystal support remains available via OSC1/OSC2 for higher precision or LIN-compliant timing, but is not required for basic functionality.

What peripheral modules are integrated into the MC908QB8VDWE?

The MC908QB8VDWE integrates the ADC10 (10-bit, 8-channel analog-to-digital converter), ESCI (Enhanced Serial Communications Interface supporting LIN 1.3), SPI (Serial Peripheral Interface), TIM (Timer Interface Module with input capture/output compare), AWU (Auto Wakeup Module), COP (Computer Operating Properly watchdog), KBI (Keyboard Interrupt Module), and LVI (Low-Voltage Inhibit). These peripherals are accessed via memory-mapped registers and share the M68HC08 CPU's unified address space.

Is the MC908QB8VDWE pin-compatible with other members of the QB8 family?

Yes, the MC908QB8VDWE is pin-compatible with the MC68HC908QB4 and MC68HC908QY8 in the same 28-pin SOIC package. All three share identical pin assignments, electrical characteristics, and peripheral I/O mapping. Differences lie in memory size (QB4 = 4 KB FLASH), peripheral inclusion (QY8 replaces ESCI with QSPI), and RAM capacity - allowing hardware reuse across variants when firmware and feature requirements align.