NXP Semiconductors MC68HC705SR3PE

Overview

MC68HC705SR3PE from Freescale is an 8-bit EPROM-based microcontroller featuring the M68HC05 CPU core, 3840-byte on-chip EPROM with security bit, 192-byte RAM (64-byte stack), 32 bidirectional I/O lines, and integrated 4-channel 8-bit ADC - used in cost-sensitive embedded control applications such as appliance motor control and industrial sensor interfaces.

For engineers reviewing the MC68HC705SR3PE datasheet, MC68HC705SR3PE pinout, MC68HC705SR3PE application, or MC68HC705SR3PE equivalent, key selection criteria include EPROM programmability, low-power STOP/WAIT/SLOW modes, keyboard interrupt support on Port A, direct LED drive capability, and compatibility with legacy MC6805R3 designs.

Technical Context

The MC68HC705SR3PE implements a fully static M68HC05 CPU core with 8-bit accumulator, index register, and condition code register, supporting inherent, immediate, direct, extended, indexed, and relative addressing modes. It executes instructions at up to 2 MHz bus frequency with crystal or RC oscillator options.

Its peripheral set includes an 8-bit countdown timer with 7-bit programmable prescaler, low-voltage reset (LVR) circuitry, and a 4-channel 8-bit successive-approximation ADC with dedicated VRH/VRL reference pins and channel assignments PD0–PD3. All I/O ports feature programmable 20 kΩ pull-ups and 10 mA sink capability.

Key Specifications

Pinout & Package

MC68HC705SR3PE is available in 40-pin plastic dual in-line package (PDIP), case 711-03, with 0.6-inch body width and 0.1-inch pin pitch. Pin functions are validated per Freescale's MC68HC05SR3D/H Rev. 2.1 documentation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC705SR3PE, the MC68HC05SR3CP trades reprogrammability for lower unit cost and guaranteed mask-ROM reliability, while the MC68HC705P6M reduces peripheral count and package size at the expense of ADC and keyboard interrupt functionality - making MC68HC705SR3PE optimal for mid-complexity embedded systems needing field-upgradable firmware and mixed-signal integration.

Availability

MC68HC705SR3PE is available at Aetrix Electronics and suitable for appliance motor control, industrial sensor interface, consumer remote control hub, and legacy equipment retrofit applications requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705SR3PE 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) was a U.S.-based semiconductor company specializing in embedded processing, analog, and connectivity solutions for automotive, industrial, and consumer markets.

The MC68HC705SR3PE belongs to the M68HC05 family - a line of cost-optimized, low-power 8-bit microcontrollers designed for resource-constrained embedded control applications where integration, reliability, and pin compatibility with legacy parts were critical.

FAQ

What is the maximum operating frequency of the MC68HC705SR3PE?

The MC68HC705SR3PE operates with a maximum bus frequency of 2 MHz, derived from its on-chip oscillator or external clock source. This corresponds to a 4 MHz instruction cycle rate for single-cycle instructions. Frequency stability depends on oscillator configuration - crystal operation yields tighter tolerance than RC networks, and actual timing must be verified under target VDD and temperature conditions per Freescale's electrical specifications table.

Does the MC68HC705SR3PE support in-circuit programming?

No, the MC68HC705SR3PE does not support in-circuit programming. It requires external EPROM programmers applying 12.5 V to the VPP pin during write/verify cycles, as specified in Appendix A of the MC68HC05SR3D/H datasheet. Programming must occur off-board in a dedicated programmer fixture; the device lacks serial or JTAG interfaces for field updates.

How many analog input channels does the MC68HC705SR3PE ADC support?

The MC68HC705SR3PE integrates a 4-channel 8-bit successive-approximation ADC, with input channels AN0–AN3 mapped to pins PD0–PD3 respectively. The ADC uses separate VRH (PD5) and VRL (PD4) reference inputs, allowing flexible full-scale range selection. Channel selection is software-controlled via the ADC Status and Control Register (ADSCR).

Is the MC68HC705SR3PE pin-compatible with the MC6805R3?

Yes, the MC68HC705SR3PE is explicitly documented as pin-compatible with the MC6805R3, enabling direct replacement in existing designs. This compatibility extends to signal routing, power/ground pin locations, and functional pin behavior - though users must verify timing margins and updated reset/interrupt behavior due to CMOS implementation differences.

What power-saving modes are available on the MC68HC705SR3PE?

The MC68HC705SR3PE supports four low-power modes: STOP (clock halted, RAM retained), WAIT (CPU halted, peripherals active), SLOW (bus frequency reduced 16×), and data-retention mode. Entry is controlled via the STOP, WAIT, and SLOW instructions; wake-up sources include RESET, IRQ, IRQ2, KBI, and timer overflow - enabling flexible energy management in battery-powered or thermally constrained systems.