NXP Semiconductors MC908QB4CDWE-NXP

Overview

MC908QB4CDWE from NXP (formerly Freescale) 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 and supports single-supply 2.7–5.5 V operation for embedded control in cost-sensitive industrial and appliance applications.

For engineers reviewing the MC908QB4CDWE datasheet, MC908QB4CDWE pinout, MC908QB4CDWE application, or MC908QB4CDWE equivalent, key selection criteria include its 20-pin SOIC-W package, internal RC oscillator with trim capability, FLASH security byte validation ($FFF6–$FFFD), and support for low-power wait/stop modes with wake-up via IRQ, KBI, or AWU.

Technical Context

The MC908QB4CDWE implements the M68HC08 CPU core with 16-bit address space, Harvard architecture instruction fetch, and 24-bit linear addressing via bank switching. Its memory map includes 4 KB FLASH (user-programmable, block-protectable), 192 B RAM, and 32 B EEPROM-like register space. The device uses a dual-clock system: internal RC oscillator (±2% accuracy, trimmable) or external crystal/ceramic resonator (1–8 MHz).

Peripherals are tightly coupled to the SIM module: ADC10 provides 10-bit conversion across 8 channels with programmable sample time; ESCI supports asynchronous serial communication with LIN-compatible framing; SPI enables master/slave synchronous data transfer; TIM offers input capture, output compare, and PWM generation; AWU delivers ultra-low-power wake-up from stop mode using programmable timeout intervals.

Key Specifications

Pinout & Package

MC908QB4CDWE is housed in a 20-pin SOIC-W (Wide) package (7.5 mm body width), RoHS-compliant, with 0.635 mm pitch and standard JEDEC MS-013AC footprint.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC908QB4CDWE, MC908QY4CDWE trades ESCI/LIN capability for improved oscillator stability and reduced peripheral count, while MC908QB8CDWE offers direct scalability in FLASH capacity without layout or firmware changes - making it the preferred upgrade path for design continuity.

Availability

MC908QB4CDWE is available at Aetrix Electronics and suitable for home appliance control, industrial sensor nodes, automotive body electronics, and consumer remote control hubs requiring stable component supply and long-term industrial availability.

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

NXP Semiconductors is a global semiconductor company formed from the spin-off of Philips' semiconductor division, now specializing in secure connectivity solutions for automotive, industrial, and IoT markets.

The MC908QB4CDWE belongs to the legacy M68HC08 microcontroller family, designed for cost-optimized, low-power embedded control in appliances, industrial panels, and automotive sub-systems where deterministic real-time response and Flash-based field-upgradability are essential.

FAQ

What is the maximum operating frequency of the MC908QB4CDWE?

The MC908QB4CDWE supports a maximum bus frequency of 8 MHz. This is achieved either by using the internal RC oscillator (trimmable to ±2%) or an external crystal/resonator in the 1–8 MHz range. The bus clock is derived directly from the selected oscillator source without internal multiplication, ensuring predictable timing behavior critical for real-time control loops and serial communication baud rate generation.

Does the MC908QB4CDWE support in-circuit debugging?

Yes, the MC908QB4CDWE supports single-wire background debug via the TEST/BKGD pin. Entry into monitor mode requires successful transmission of eight user-defined security bytes matching those programmed at memory locations $FFF6–$FFFD. An enhanced security function denies monitor mode entry if five or more of those bytes are zero, preventing accidental or unauthorized access during development or field service.

What peripheral modules are integrated into the MC908QB4CDWE?

The MC908QB4CDWE integrates the ADC10 (10-bit, 8-channel analog-to-digital converter), ESCI (Enhanced Serial Communications Interface with LIN framing), SPI (Serial Peripheral Interface), TIM (Timer Interface Module with input capture/output compare), AWU (Auto Wakeup Module), COP (Computer Operating Properly watchdog), and KBI (Keyboard Interrupt Module). All modules are managed through the System Integration Module (SIM) and share common clock and reset resources.

How does the FLASH security feature work on the MC908QB4CDWE?

The MC908QB4CDWE FLASH security feature prevents unauthorized read access to program memory during monitor mode. To enter monitor mode, the host must send eight security bytes that exactly match the values stored at FLASH addresses $FFF6–$FFFD. These locations must be programmed - leaving them blank or setting five or more bytes to zero will block monitor mode entry, enforcing secure firmware protection in deployed systems.

Is the MC908QB4CDWE pin-compatible with other members of the QB-series?

Yes, the MC908QB4CDWE is pin-compatible with the MC908QB8CDWE and shares the same 20-pin SOIC-W package and pin assignments. This allows direct PCB-level replacement with increased FLASH capacity (8 KB vs. 4 KB) without layout modification. However, it is not pin-compatible with the QY-series (e.g., MC908QY4CDWE), which differs in peripheral mapping and oscillator configuration despite identical packaging.