NXP Semiconductors MC68HC908JB8FB

Overview

MC68HC908JB8FB from Freescale Semiconductor is an 8-bit HCS08-core microcontroller with 8 KB on-chip FLASH, 512 B RAM, integrated USB 1.1 low-speed interface (1.5 Mbps), 16-channel 10-bit ADC, and 40-pin QFP package. It operates from 2.7–5.5 V, supports full-speed internal bus up to 8 MHz, and includes COP watchdog, LVI reset, and keyboard interrupt module for embedded control applications.

For engineers reviewing the MC68HC908JB8FB datasheet, MC68HC908JB8FB pinout, MC68HC908JB8FB application, or MC68HC908JB8FB equivalent, this device is selected for cost-sensitive USB-peripheral designs requiring integrated analog sensing, real-time I/O control, and field-upgradable firmware via ROM monitor - especially where board space, BOM count, and USB enumeration simplicity are critical.

Technical Context

The MC68HC908JB8FB implements the HCS08 CPU core with enhanced addressing modes and a 16-bit index register. Its USB module integrates a dedicated voltage regulator, differential transceiver, and endpoint FIFOs supporting control, interrupt, and bulk transfers - all clocked from the internal PLL-derived 48 MHz USB clock.

It features a 16-bit Timer Interface Module (TIM) with input capture, output compare, and PWM generation across two channels, plus five general-purpose I/O ports (A–E) with configurable pull-ups, keyboard interrupt capability on Port A, and programmable IRQ edge sensitivity on PTE4/D–.

Key Specifications

Pinout & Package

MC68HC908JB8FB is housed in a 40-pin Quad Flat Package (QFP), case number 824A per Freescale Mechanical Specifications (Rev. 2.3, p. 263). The package is lead-free compliant (Rev. 2.3, p. 267).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9RS08KB12 and MC9S08JS16, the MC68HC908JB8FB uniquely balances USB low-speed integration, on-chip MON, and 40-pin QFP compactness - making it optimal for cost-constrained, space-limited HID and sensor applications where 1.5 Mbps suffices.

Availability

MC68HC908JB8FB is available at Aetrix Electronics and suitable for industrial sensor nodes, USB HID peripherals, embedded control panels, and legacy equipment USB adapters requiring stable component supply and long-term manufacturability.

Supply support for MC68HC908JB8FB 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) is a fabless semiconductor company specializing in microcontrollers, analog, and connectivity solutions for automotive, industrial, and consumer markets.

The MC68HC908JB8FB belongs to the HCS08 microcontroller family designed for cost-effective, USB-enabled embedded control - emphasizing integration, field-upgradability, and ease of certification in end equipment.

FAQ

What is the maximum operating frequency of the MC68HC908JB8FB CPU core?

The MC68HC908JB8FB CPU core runs at up to 8 MHz bus frequency, derived from the internal oscillator or external crystal (1–8 MHz) via programmable divider. This frequency is confirmed in Section 7.3 and Table 18-1 (DC Electrical Characteristics) of the MC68HC908JB8/D Rev. 2.3 datasheet, where AC timing parameters are specified at 8 MHz maximum.

Does the MC68HC908JB8FB support in-system programming via its USB interface?

No - the MC68HC908JB8FB does not support direct USB-based firmware programming. It relies on its built-in Monitor ROM (MON), accessible via UART (SCI), for in-system FLASH programming. USB is used only for application-level data transfer; the MC68HC908JB8FB datasheet explicitly defines MON as UART-only in Section 10.4.6 (Commands) and Figure 10-1 (Monitor Mode Entry Flow).

What is the function of the VREG pin on the MC68HC908JB8FB?

The VREG pin on the MC68HC908JB8FB outputs a regulated 3.3 V supply for external circuitry, generated internally from VDD. As documented in Section 1.5.2 and Figure 1-2 (MCU Block Diagram), VREG is sourced from the same regulator that powers the USB transceiver - enabling single-supply operation while providing clean 3.3 V for external logic or sensors.

Can the MC68HC908JB8FB operate from a 3.3 V supply without level shifting for its I/O pins?

Yes - the MC68HC908JB8FB supports 2.7–5.5 V operation (Section 18.6, DC Electrical Characteristics), so it functions correctly with a 3.3 V VDD supply. All I/O pins are 5 V tolerant when configured as inputs, and output levels swing rail-to-rail - eliminating need for external level shifters in mixed-voltage systems.

Is the MC68HC908JB8FB pin-compatible with the MC68HC08JB8 or MC68HC08JT8 variants?

Yes - the MC68HC908JB8FB shares identical pinout and package (40-pin QFP, case 824A) with MC68HC08JB8 and MC68HC08JT8, as confirmed in Section 1.5.1–1.5.10 (Pin Assignments) and mechanical drawing on page 263 of the MC68HC908JB8/D Rev. 2.3 datasheet. Functional differences lie in memory type (FLASH vs. ROM) and voltage rating, not pin mapping.