NXP Semiconductors MC908QB4CDWE

Overview

MC908QB4CDWE 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, and COP watchdog. It operates at up to 8 MHz bus frequency, supports internal/external clock sources, and targets low-power embedded control in industrial sensors and appliance subsystems.

For engineers reviewing the MC908QB4CDWE datasheet, MC908QB4CDWE pinout, MC908QB4CDWE application, or MC908QB4CDWE equivalent, this page delivers verified technical context, package mapping, security byte configuration guidance, and real-world use-case validation for production design-in and legacy system maintenance.

Technical Context

The MC908QB4CDWE implements the M68HC08 CPU core with 16-bit address space, Harvard architecture memory organization, and a 2-stage pipeline. Its FLASH memory includes block protection and mass erase capability, while the ADC10 module provides 10-bit resolution with programmable sample time and 8-channel analog input multiplexing.

Security enforcement occurs during monitor mode entry: host must supply eight user-defined bytes matching locations $FFF6–$FFFD; entry is denied if five or more of those bytes are $00. The device supports multiple low-power modes (Wait/Stop) with configurable wake-up sources including IRQ, KBI, and AWU timer events.

Key Specifications

Pinout & Package

MC908QB4CDWE is housed in a 28-pin SOIC (Small Outline Integrated Circuit) package with 24 I/O pins, power, ground, oscillator, and reset terminals. Pin functions include dual-purpose port pins supporting digital I/O, ADC inputs, serial interfaces, and interrupt sources.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC908QB4CDWE, the QB8 variant offers double FLASH capacity without layout change, while the QY4 variant sacrifices I/O and serial capability for smaller footprint-neither is pin-compatible with MC908QB4CDWE beyond shared family architecture.

Availability

MC908QB4CDWE is available at Aetrix Electronics and suitable for industrial sensor nodes, home appliance control units, and smart meter subsystems requiring stable component supply across extended product lifecycles.

Supply support for MC908QB4CDWE 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 MCU innovation for automotive and industrial markets, emphasizing robustness, low-power operation, and toolchain maturity.

The MC68HC08 family-including MC908QB4CDWE-was designed for cost-sensitive, reliability-critical embedded control applications where deterministic real-time response and flash-based field update capability are essential.

FAQ

What is the maximum operating frequency of the MC908QB4CDWE?

The MC908QB4CDWE supports a maximum bus clock frequency of 8 MHz. This corresponds to an instruction execution rate of approximately 2 million instructions per second (MIPS), assuming typical 4-cycle instruction timing. The internal oscillator is factory-trimmed to 4.194 MHz ±2%, and external crystals up to 8 MHz may be used with appropriate load capacitance and stability considerations.

Does the MC908QB4CDWE support in-circuit debugging?

Yes, the MC908QB4CDWE supports monitor mode entry via the BKGD pin for non-intrusive debugging and programming. Entry requires correct 8-byte security vector at $FFF6–$FFFD; if five or more bytes are $00, monitor access is denied. Debugging tools must comply with Freescale's HCS08 monitor protocol, and the BKGD pin serves dual function as I/O when monitor mode is inactive.

How is FLASH memory protected on the MC908QB4CDWE?

FLASH protection on the MC908QB4CDWE is implemented through the FLASH Block Protect Register (FBPROT), which allows selective locking of 512-byte blocks. Once protected, blocks cannot be erased or programmed without a full mass erase. Additionally, security bytes at $FFF6–$FFFD prevent unauthorized monitor-mode access to FLASH contents, enforcing firmware confidentiality during development and field service.

Can the MC908QB4CDWE operate from a 3.3 V supply?

Yes, the MC908QB4CDWE operates across a supply voltage range of 2.7 V to 5.5 V, making it fully compatible with 3.3 V systems. At 3.3 V, the maximum guaranteed bus frequency is 6 MHz per electrical specifications; operation at 8 MHz requires ≥4.5 V supply. I/O pins are 5 V tolerant when configured as inputs, simplifying interface with mixed-voltage peripherals.

What peripheral modules are integrated into the MC908QB4CDWE?

The MC908QB4CDWE integrates the ADC10 (10-bit, 8-channel), ESCI (UART with LIN support), SPI, TIM (16-bit timer with input capture/output compare), AWU (programmable wake-up timer), COP (watchdog), KBI (keyboard interrupt), and LVI (brown-out detection) modules. All share the M68HC08 core and memory map, with register-level compatibility across the QB-series family.