NXP Semiconductors MC908SR12MFAE

Overview

MC908SR12MFAE from Freescale Semiconductor is an 8-bit HCS08 microcontroller with 12 KB on-chip FLASH, 512 B RAM, and integrated analog peripherals including a 10-bit ADC, two-stage amplifier, current detection circuit, and temperature sensor. It features a PLL-based clock generator (up to 20 MHz core), SCI, I²C, PWM, TIM, and TBM modules, and operates from 2.7–5.5 V. It targets embedded control in industrial sensors and motor feedback systems.

For engineers reviewing the MC908SR12MFAE datasheet, MC908SR12MFAE pinout, MC908SR12MFAE application, or MC908SR12MFAE equivalent, key selection criteria include its 44-pin LQFP package, 10-bit ADC with auto-scan mode, integrated current flow detection amplifier, PLL clock generation with CGMXFC filter capacitor support, and ROM-based monitor mode for in-system programming.

Technical Context

The MC908SR12MFAE implements the HCS08 CPU core with 8-bit architecture, supporting wait/stop low-power modes and break interrupt handling via dedicated BRK module. Its Clock Generator Module integrates a PLL with programmable multiplier (×1 to ×32), reference divider, VCO range select, and external filter capacitor (CGMXFC) interface for stable frequency synthesis.

The analog subsystem includes a two-stage amplifier with configurable gain, a dedicated current flow detection amplifier with trip-point threshold, and a 10-bit successive-approximation ADC with 8-channel input multiplexing, auto-scan capability, and result justification control - all operating from separate analog supply pins (VDDA/VSSA).

Key Specifications

Pinout & Package

MC908SR12MFAE is housed in a 44-pin LQFP (7 mm × 7 mm, 0.8 mm pitch) package with exposed thermal pad. Power, ground, oscillator, reset, and peripheral I/O are distributed across four sides for balanced PCB routing and noise isolation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC908SR12MFAE, MC9RS08KA2CFKR offers lower cost and smaller size but sacrifices analog integration and clock flexibility, while S9KEAZ128AMLH delivers greater processing headroom and memory but increases BOM complexity and power consumption for equivalent analog sensing tasks.

Availability

MC908SR12MFAE is available at Aetrix Electronics and suitable for industrial motor control, smart sensor nodes, power supply monitoring, and appliance safety controllers requiring stable component supply and long-term lifecycle support.

Supply support for MC908SR12MFAE 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) designed industry-grade microcontrollers for automotive, industrial, and consumer applications with emphasis on mixed-signal integration and robustness.

The MC908SR12MFAE belongs to the HCS08 family, engineered for cost-sensitive embedded control where analog signal acquisition, real-time PWM generation, and low-power operation are critical - especially in motor feedback and sensor conditioning applications.

FAQ

What is the maximum operating frequency of the MC908SR12MFAE core?

The MC908SR12MFAE achieves a maximum core frequency of 20 MHz using its integrated Phase-Locked Loop (PLL) with programmable multiplier and external crystal or RC oscillator input. The PLL allows flexible clock scaling from base frequencies of 1–8 MHz, and the CGMXFC pin must be connected to an external RC filter to ensure stable lock and low jitter. This 20 MHz operation is confirmed in Section 8.4.2 and Table 24-2 of the Rev. 5.0 datasheet.

Does the MC908SR12MFAE include an on-chip temperature sensor?

Yes, the MC908SR12MFAE includes an integrated on-die temperature sensor usable via the ADC input channel ATD0 (OPIN1). As documented in Section 14.4.1, it provides factory-calibrated output with ±5°C accuracy across the operating temperature range (−40°C to +105°C), enabling thermal monitoring without external components. The sensor output connects directly to the analog front-end, and readings are acquired using the same 10-bit ADC used for other analog inputs.

How does the current flow detection amplifier in the MC908SR12MFAE function?

The MC908SR12MFAE features a dedicated current flow detection amplifier with programmable trip point, described in Section 14.4.4–14.4.5. It compares sensed current against an internal reference and asserts a digital output signal (CFDOUT) when threshold is exceeded. This signal can trigger IRQ interrupts or be polled via GPIO, enabling sub-microsecond overcurrent response without CPU intervention. Its design eliminates the need for external comparator circuits in motor driver protection schemes.

Can the MC908SR12MFAE be programmed in-system without an external debugger?

Yes, the MC908SR12MFAE includes a factory-programmed Monitor ROM (MON) that enables UART-based in-system programming and debugging. As detailed in Section 10, the MON module supports flash erase/write commands over SCI using standard ASCII protocols, requiring only a UART interface and no JTAG or BDM hardware. This capability is accessible via PTA1/PTA2 timing-controlled entry sequence and is fully functional in the MC908SR12MFAE variant.

What analog reference configurations does the MC908SR12MFAE support for its ADC?

The MC908SR12MFAE supports flexible ADC reference configuration via dedicated VREFH and VREFL pins. These may be tied to VDDA/VSSA for ratiometric measurement, connected to external precision references, or configured for internal bandgap-derived references (Section 15.4.2). The ADC's 10-bit resolution and left/right-justified result storage (ADRH0/ADRL0) allow direct mapping to sensor transfer functions without software bit-shifting, and the dual-reference design ensures immunity to supply ripple in noisy industrial environments.