NXP Semiconductors MC68HC705SR3CP

Overview

MC68HC705SR3CP from Freescale is an 8-bit EPROM-based microcontroller with 3840 bytes of on-chip EPROM, 192 bytes of RAM, and integrated peripherals including an 8-bit ADC (4-channel), 8-bit countdown timer with 7-bit prescaler, keyboard interrupt capability, and programmable I/O ports. It operates at up to 4 MHz bus frequency and supports STOP/WAIT/SLOW low-power modes for battery-powered instrumentation and control applications.

For engineers reviewing the MC68HC705SR3CP datasheet, MC68HC705SR3CP pinout, MC68HC705SR3CP application, or MC68HC705SR3CP equivalent, key selection criteria include its 40-pin PDIP package, EPROM programmability, 5V/3V dual-voltage operation, built-in oscillator with RC/crystal options, and direct LED drive capability on all I/O pins.

Technical Context

The MC68HC705SR3CP implements the M68HC05 CPU core with a static design supporting zero-wait-state operation across its full voltage and temperature range. Its memory map includes 3840-byte user EPROM with security bit, 240-byte bootstrap/self-check ROM, and 192-byte RAM (64-byte stack). The device uses a single-phase clock derived from an internal oscillator with selectable crystal, RC, or external clock input.

Peripheral integration includes a 4-channel 8-bit successive-approximation ADC with dedicated analog inputs on Port D (PD0–PD3), a timer with gating via the TIMER pin, and two external interrupt lines (IRQ and IRQ2 on PD6). All 32 I/O lines support programmable pull-up resistors (20 kΩ) and direct LED drive (10 mA sink per port A pin).

Key Specifications

Pinout & Package

MC68HC705SR3CP is housed in a 40-pin Plastic Dual In-line Package (PDIP), Case 711-03, with 0.6-inch body width and 0.1-inch pin pitch. Pin assignments conform to standard MC68HC05SR3 layout, with VDD (pin 4), VSS (pins 1, 5), RESET (pin 2), IRQ (pin 3), OSC1/OSC2 (pins 5/6), and Port A (pins 33–40) as primary functional groups.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC05SR3CP and MC68HC705P6CP, the MC68HC705SR3CP uniquely balances EPROM reprogrammability, integrated ADC, and full 32-pin I/O in a 40-pin PDIP-making it optimal for mid-complexity embedded systems requiring analog interface and firmware iteration.

Availability

MC68HC705SR3CP is available at Aetrix Electronics and suitable for industrial control panels, portable medical instruments, home appliance timers, and automotive body control subsystems requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705SR3CP 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 leading designer of embedded processors and analog/mixed-signal ICs, focused on automotive, industrial, and networking applications.

The MC68HC705SR3CP belongs to the M68HC05 family-a line of cost-optimized, low-power 8-bit microcontrollers targeting appliance, instrumentation, and control applications where integration, reliability, and ease of use were prioritized over raw performance.

FAQ

What is the maximum operating frequency of the MC68HC705SR3CP?

The MC68HC705SR3CP supports a maximum bus frequency of 4 MHz, corresponding to an 8 MHz crystal input (since the internal oscillator divides by 2). This frequency is valid across the full specified temperature and voltage range (−40°C to +85°C, 3.0–5.5 V), enabling deterministic real-time response in time-critical control loops without external clock scaling.

Does the MC68HC705SR3CP support in-circuit programming?

No, the MC68HC705SR3CP requires external EPROM programming equipment applying 12.5 V to the VPP pin (pin 7); it does not support in-system or in-circuit programming. Programming must be performed before soldering, using a dedicated EPROM programmer compatible with M68HC05-family timing and voltage sequences.

How many analog input channels does the MC68HC705SR3CP ADC support?

The MC68HC705SR3CP integrates a 4-channel 8-bit successive-approximation ADC mapped to PD0 through PD3 (pins 24–27). Each channel accepts 0–VDD input range and provides conversion results in the ADDR register; no external sample-and-hold or reference components are required for basic sensor interfacing.

What low-power modes are available on the MC68HC705SR3CP?

The MC68HC705SR3CP offers three hardware-controlled low-power modes: STOP (µA-level current, all clocks halted, wake via RESET/IRQ), WAIT (reduced current, main clock stopped, wake via IRQ), and SLOW (bus clock divided by 16, full functionality retained at reduced speed). These enable flexible power management tailored to application duty cycles.

Is the MC68HC705SR3CP pin-compatible with earlier MC6805R3 designs?

Yes, the MC68HC705SR3CP is fully pin-compatible with the MC6805R3, allowing drop-in replacement in existing designs. This compatibility extends to signal mapping, power pin locations, and reset/interrupt pin functions-enabling immediate power-efficiency and peripheral integration upgrades without PCB revision.