NXP Semiconductors MC908QB4MDWE

Overview

MC908QB4MDWE from Freescale Semiconductor is an 8-bit M68HC08 core microcontroller with 4 KB on-chip FLASH, 192 B RAM, and integrated peripherals including ADC10, ESCI, SPI, TIM, AWU, COP, and KBI. It operates at up to 8 MHz bus frequency, supports 5 V operation, and features internal oscillator trimming and flash security via user-programmable $FFF6–$FFFD bytes.

For engineers reviewing the MC908QB4MDWE datasheet, MC908QB4MDWE pinout, MC908QB4MDWE application, or MC908QB4MDWE equivalent, this page delivers verified functional specifications, validated package mapping (SOIC-28), confirmed security byte behavior, real-world low-power use cases, and two field-tested alternative parts for design continuity.

Technical Context

The MC908QB4MDWE implements the M68HC08 CPU core with 16-bit address space, Harvard architecture memory organization, and a unified interrupt vector table. Its flash memory supports in-system programming with mass and page erase, while the ADC10 module provides 10-bit resolution across 8 channels with programmable sample time and conversion trigger sources.

Security enforcement occurs during monitor mode entry: host must supply eight matching bytes to locations $FFF6–$FFFD; entry is denied if five or more of those bytes are zero. The internal oscillator supports trim register adjustment for ±2% accuracy across temperature and voltage, and clock switching between internal RC and external crystal is fully controlled by OSC module registers.

Key Specifications

Pinout & Package

MC908QB4MDWE is housed in a 28-pin SOIC (Small Outline Integrated Circuit) package with 0.300-inch body width and standard 1.27 mm pitch. Pin assignments follow the MC68HC908QB8/QB4 family layout, with shared port pins supporting multiple functions including I/O, analog input, serial interface, and reset.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC908QB4MDWE, the MC908QB8MDWE offers direct code compatibility and doubled FLASH capacity without layout changes, while the MC9RS08KB2CPD requires full firmware rework and sacrifices key low-power and interface features - making it a functional alternative only under strict cost constraints.

Availability

MC908QB4MDWE is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor nodes, home appliance control, and portable medical devices requiring stable component supply and long-term manufacturability.

Supply support for MC908QB4MDWE 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) was a leading designer of embedded processors, analog, and mixed-signal ICs for automotive, industrial, and consumer markets.

The MC68HC908QB4 belongs to the M68HC08 microcontroller family, engineered for cost-sensitive, low-power 8-bit control applications requiring integrated analog interfaces, serial communications, and robust flash security - especially in automotive and industrial environments.

FAQ

What is the maximum bus frequency supported by the MC908QB4MDWE?

The MC908QB4MDWE supports a maximum bus frequency of 8 MHz. This is achieved either through the internal RC oscillator (calibrated via the trim register) or an external crystal connected to OSC1/OSC2. The actual bus speed depends on the selected clock source and configuration bits in the OSC and CONFIG registers, and must remain within the 4.5–5.5 V supply range for guaranteed operation.

Does the MC908QB4MDWE include hardware support for LIN communication?

Yes, the MC908QB4MDWE's Enhanced Serial Communications Interface (ESCI) module supports LIN 1.3 physical layer requirements, including break detection, sync field generation, and auto-baud rate detection. While it does not implement the full LIN protocol stack in hardware, its ESCI provides the precise timing and framing control needed for reliable LIN slave node operation in automotive body electronics.

How does the flash security feature work on the MC908QB4MDWE?

The MC908QB4MDWE enforces flash security during monitor mode entry: the host must send eight bytes matching the values stored at memory addresses $FFF6–$FFFD. If five or more of those bytes are $00, monitor mode entry is denied. This prevents unauthorized readout of protected firmware, and users must explicitly program these locations-even if unused-to avoid accidental security lockout.

Can the MC908QB4MDWE operate without an external crystal?

Yes, the MC908QB4MDWE can operate entirely from its internal RC oscillator, which is factory-trimmed and further adjustable via the OSCTRIM register. This allows full functionality-including ADC conversions, ESCI communication, and COP watchdog operation-at up to 8 MHz bus speed without any external timing components, reducing BOM cost and board space in cost-sensitive designs.

What low-power modes are supported by the MC908QB4MDWE?

The MC908QB4MDWE supports Wait and Stop modes. In Wait mode, the CPU halts but peripherals (ADC, ESCI, TIM) remain active; in Stop mode, nearly all clocks are disabled except the AWU's RC oscillator, achieving sub-1 µA current draw. Both modes retain RAM contents, and wake-up sources include IRQ, KBI, AWU timeout, and reset - enabling flexible power management for battery-operated devices.