NXP Semiconductors MC68HC908SR12CB

Overview

MC68HC908SR12CB from NXP (formerly Freescale) is an 8-bit HCS08 microcontroller with 12 KB on-chip FLASH, 512 B RAM, and integrated analog peripherals including a 10-bit ADC with auto-scan, two PWM modules, SCI and I²C interfaces, and a PLL-based clock generator. It operates at up to 8 MHz bus frequency and targets embedded control in industrial sensors, motor drives, and appliance subsystems.

For engineers reviewing the MC68HC908SR12CB datasheet, MC68HC908SR12CB pinout, MC68HC908SR12CB application, or MC68HC908SR12CB equivalent, key selection criteria include its 44-pin LQFP package, 3–5.5 V supply range, on-chip voltage regulator support, monitor ROM for in-system programming, and dual PWM channels with automatic phase control.

Technical Context

The MC68HC908SR12CB implements the HCS08 CPU core with enhanced addressing modes and a 16-bit index register. Its Clock Generator Module (CGM) integrates a PLL with programmable multiplier (×1 to ×32), reference divider, and VCO range select-enabling precise bus clock derivation from low-frequency crystals or RC oscillators.

The analog subsystem includes a dedicated 10-bit ADC with 8 input channels, configurable reference (VREFH/VREFL), and auto-scan mode storing results in ADRL1–ADRL3 registers. The dual PWM module supports buffered/unbuffered outputs, independent period/phase control, and synchronization with TIM or TBM modules.

Key Specifications

Pinout & Package

MC68HC908SR12CB is housed in a 44-pin LQFP (7 mm × 7 mm, 0.8 mm pitch) package with exposed thermal pad. Pin assignments follow Freescale's standard HCS08 SR-series layout, including dedicated analog power (VDDA/VSSA), ADC reference (VREFH/VREFL), and CGM filter (CGMXFC) terminals.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC9RS08KA2, the MC68HC908SR12CB delivers significantly richer analog and communication resources in the same 44-pin LQFP package; versus S9KEAZ128AMLH, it offers lower power consumption in stop mode and simpler toolchain requirements for deterministic real-time control.

Availability

MC68HC908SR12CB is available at Aetrix Electronics and suitable for industrial sensor nodes, appliance motor controllers, smart power outlets, and building automation systems requiring stable component supply, long-term lifecycle support, and consistent parametric performance across production batches.

Supply support for MC68HC908SR12CB 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, and IoT applications, with roots in Freescale's microcontroller heritage.

The MC68HC908SR12CB belongs to the HCS08 family, designed specifically for cost-sensitive, resource-constrained embedded control applications requiring robust analog integration, low-voltage operation, and field-programmable FLASH in compact packages.

FAQ

What is the maximum operating frequency of the MC68HC908SR12CB bus clock?

The MC68HC908SR12CB supports a maximum bus clock frequency of 8 MHz. This is achieved using the integrated PLL with programmable multiplier settings (e.g., ×16 from a 500 kHz reference). The PLL allows stable high-speed operation even with low-frequency, low-cost crystals, and its bandwidth is configurable via the PLL Bandwidth Control Register to balance lock time and jitter performance. The MC68HC908SR12CB datasheet specifies timing parameters only up to 8 MHz.

Does the MC68HC908SR12CB support in-system programming without external hardware?

Yes, the MC68HC908SR12CB includes a 1 KB Monitor ROM (MON) that enables in-system programming via the SCI interface using standard UART commands. This eliminates the need for external programmers during development or field updates. Entry into monitor mode is triggered by asserting RST while holding PTA1 and PTA2 low, and the MC68HC908SR12CB responds with a handshake character before accepting flash write/erase commands.

How many ADC input channels does the MC68HC908SR12CB support, and what is the resolution?

The MC68HC908SR12CB features a 10-bit successive-approximation ADC with 8 selectable input channels (ATD0–ATD7), mapped to pins OPIN1/ATD0 through OPIN8/ATD7. Conversion results are stored in 16-bit registers (ADRH0/ADRL0 and ADRL1–ADRL3 in auto-scan mode), and the ADC supports both single-conversion and continuous auto-scan modes with configurable sample time and justification. The MC68HC908SR12CB datasheet confirms full 10-bit linearity and monotonicity across the specified operating range.

What low-power modes are available on the MC68HC908SR12CB, and how do they affect peripheral operation?

The MC68HC908SR12CB supports Wait and Stop modes. In Wait mode, the CPU halts but the bus clock remains active, allowing peripherals like TIM, ADC, and SCI to continue operation and generate interrupts. In Stop mode, the bus clock stops entirely; only asynchronous events (IRQ1, KBI, LVI, COP timeout) can wake the device. RAM contents are retained in both modes, and the MC68HC908SR12CB's Low-Voltage Inhibit circuit remains functional in Stop mode to prevent corruption during brown-out conditions.

Can the MC68HC908SR12CB generate complementary PWM outputs with dead-time insertion?

No, the MC68HC908SR12CB does not include hardware dead-time insertion or complementary PWM output pairs. Its two PWM modules operate independently with programmable period and duty cycle, but outputs are non-inverting and lack synchronized complementary generation. Dead-time must be implemented in software using TIM capture/compare events or external logic. This limitation is documented in Section 13.4 and Figure 13-1 of the MC68HC908SR12CB datasheet, which shows only single-ended PWM waveform generation.