NXP Semiconductors MC68HC908AP64CB

Overview

MC68HC908AP64CB from NXP (formerly Freescale) is an 8-bit HCS08-core microcontroller with 64 KB on-chip Flash, 2 KB RAM, and integrated peripherals including SCI, SPI, I²C, ADC, PWM, and TIM modules. It operates at up to 8 MHz CPU frequency with internal oscillator options and supports 5 V or 3 V supply. Used in industrial control panels requiring deterministic real-time response and field-upgradable firmware.

For engineers reviewing the MC68HC908AP64CB datasheet, MC68HC908AP64CB pinout, MC68HC908AP64CB application, or MC68HC908AP64CB equivalent, key selection criteria include Flash endurance (10k erase/write cycles), 8-channel 10-bit ADC with configurable clock (500 kHz–1 MHz), low-power stop/wait modes, and ROM-based monitor for in-system programming without external debugger.

Technical Context

The MC68HC908AP64CB implements the HCS08 CPU core with 16-bit address bus and Harvard architecture, supporting indexed, extended, and relative addressing modes. Its Clock Generator Module (CGM) integrates a PLL for frequency multiplication and selectable reference clocks (internal RC, crystal, or external). The System Integration Module (SIM) manages reset sources-including COP watchdog, LVI, and illegal opcode-and coordinates interrupt prioritization across 27 vector locations.

Peripheral integration includes a 16-bit Timer Interface Module (TIM) with input capture, output compare, and buffered/unbuffered PWM; a Serial Communications Interface (SCI) compliant with RS-232/RS-485 framing; and a Multi-Master IIC interface supporting standard-mode (100 kbps) and fast-mode (400 kbps) operation. All modules are memory-mapped and accessible via dedicated control/status registers.

Key Specifications

Pinout & Package

MC68HC908AP64CB is housed in a 64-pin LQFP (10 mm × 10 mm, 0.5 mm pitch) package with exposed thermal pad. Pin functions include dual-purpose GPIO (up to 54 I/O), dedicated peripheral signals (SCI TX/RX, SPI SCK/MOSI/MISO, I²C SCL/SDA), analog inputs (ADC0–ADC7), and power/ground distribution optimized for noise immunity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9S08AW64 and S9KEAZ128AMLH, the MC68HC908AP64CB offers unique value in legacy-compatible, cost-sensitive industrial systems where ROM-based in-field updates, integrated VREG, and deterministic 8-bit real-time behavior outweigh raw performance or protocol expansion needs.

Availability

MC68HC908AP64CB is available at Aetrix Electronics and suitable for industrial motor control, smart sensor nodes, PLC I/O modules, and medical infusion pump controllers requiring stable component supply and long-term lifecycle support.

Supply support for MC68HC908AP64CB 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 leader focused on secure connectivity solutions for automotive, industrial, IoT, and mobile applications.

The MC68HC908AP64CB belongs to the legacy HCS08 microcontroller family designed for cost-effective, low-power embedded control in industrial automation, building systems, and medical devices where reliability and long-term availability are critical.

FAQ

What is the maximum operating frequency of the MC68HC908AP64CB?

The MC68HC908AP64CB supports a maximum CPU bus frequency of 8 MHz. This is achieved using the internal Phase-Locked Loop (PLL) circuit within the Clock Generator Module (CGM), which multiplies the base oscillator frequency. The device can operate directly from its internal RC oscillator (typically 31.25 kHz or 1 MHz) or from an external crystal (1–8 MHz), with PLL settings allowing scalable system clock derivation while maintaining timing integrity across all peripherals. The MC68HC908AP64CB's timing specifications are fully characterized up to this 8 MHz limit.

Does the MC68HC908AP64CB support in-system programming without external hardware?

Yes, the MC68HC908AP64CB includes a 1 KB Monitor ROM (MON) that enables full in-system programming (ISP) via its Serial Communications Interface (SCI) using only a UART connection-no external programmer or debug probe required. The MON firmware supports Flash erase, program, and verify operations, along with security lock/unlock commands. Entry into monitor mode is triggered by asserting the BKGD pin during reset or via a break signal on SCI, and the MC68HC908AP64CB retains this capability even after Flash security is enabled, provided the security byte has not been programmed to disable MON access.

What are the low-power modes supported by the MC68HC908AP64CB?

The MC68HC908AP64CB supports two primary low-power modes: Wait and Stop. In Wait mode, the CPU halts but the bus clock remains active, allowing peripherals like TIM, SCI, and ADC to continue operation and generate interrupts. In Stop mode, nearly all clocks are disabled-including the CGM and peripheral clocks-reducing current consumption to ≤1.0 µA (typical at 3 V). Wake-up from Stop mode occurs via external interrupt (IRQ), keyboard interrupt (KBI), or reset. Both modes are controlled via the STOP and WAIT instructions and are fully documented in Chapter 4 and Chapter 7 of the MC68HC908AP64CB datasheet.

How does the internal voltage regulator (VREG) function on the MC68HC908AP64CB?

The VREG pin on the MC68HC908AP64CB provides a regulated 3.3 V output derived from the main VDD supply (typically 5 V), enabling mixed-voltage I/O operation without external regulators. When enabled via the CONFIG1 register, VREG powers internal logic and can drive external 3.3 V peripherals. It supports bypass capacitor filtering (recommended 1 µF ceramic) and includes over-current and thermal shutdown protection. The MC68HC908AP64CB's VREG is not intended as a high-current supply-it delivers up to 10 mA-and must be decoupled locally to maintain ADC reference stability and digital noise immunity.

Is the MC68HC908AP64CB pin-compatible with other members of the AP family?

Yes, the MC68HC908AP64CB shares identical pinout and package (64-pin LQFP) with MC68HC908AP32CB, MC68HC908AP16CB, and MC68HC908AP8CB, enabling hardware reuse across memory variants. Differences are limited to Flash size (64 KB vs. 32/16/8 KB), RAM capacity (2 KB vs. 1.5/1/0.5 KB), and corresponding memory map allocation-all transparent to PCB layout and peripheral routing. This pin compatibility allows scalable product families with common schematics and layouts, reducing design validation effort and inventory complexity for the MC68HC908AP64CB and its siblings.