NXP Semiconductors MC68HC705SR3CPE

Overview

MC68HC705SR3CPE from Freescale is an 8-bit EPROM-based microcontroller with 3840-byte on-chip EPROM, 192-byte RAM, 32 bidirectional I/O lines, integrated 4-channel 8-bit ADC, and 8-bit programmable timer. It features STOP/WAIT/SLOW low-power modes, keyboard interrupt capability (KBI) on Port A, and direct LED drive support - used in cost-sensitive industrial control and appliance timing systems.

For engineers reviewing the MC68HC705SR3CPE datasheet, MC68HC705SR3CPE pinout, MC68HC705SR3CPE application, or MC68HC705SR3CPE equivalent, key selection considerations include EPROM programmability, 40-pin PDIP package compatibility, 5 V/3 V dual-voltage operation, and mask-configurable power-on reset delay options up to 32768 cycles.

Technical Context

The MC68HC705SR3CPE implements the M68HC05 CPU core with 8-bit accumulator, index register, and condition code register, supporting inherent, immediate, direct, extended, and indexed addressing modes. Its instruction set includes bit manipulation, read-modify-write, and software interrupt (SWI) instructions.

It integrates a crystal/RC oscillator with internal capacitors, low-voltage reset (LVR), and two external interrupt sources (IRQ and IRQ2 on PD6). The ADC supports four single-ended channels (PD0–PD3) with configurable reference (VRL/VRH), while Timer uses a 7-bit prescaler feeding an 8-bit down-counter gated by the TIMER pin.

Key Specifications

Pinout & Package

MC68HC705SR3CPE 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 follow standard M68HC05SR3 layout with dedicated OSC1/OSC2, IRQ, RESET, TIMER, VDD, VSS, and 32 I/O lines across Ports A–D.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MC68HC05SR3CPE and MC68HC705P6CPE, the MC68HC705SR3CPE uniquely balances EPROM field-programmability, 40-pin PDIP compatibility, and integrated KBI/ADC - making it optimal for cost-constrained upgrades where PCB reuse is mandatory.

Availability

MC68HC705SR3CPE is available at Aetrix Electronics and suitable for home appliance control, industrial HMI panels, small-motor drive modules, and legacy equipment upgrades requiring stable component supply and long-term obsolescence management.

Supply support for MC68HC705SR3CPE 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 controllers, analog, and connectivity solutions for automotive, industrial, and consumer markets.

The MC68HC705SR3CPE belongs to the M68HC05 family - designed specifically for cost-sensitive, low-power 8-bit control applications where integration of ADC, KBI, and programmable I/O reduced external component count.

FAQ

What is the maximum operating frequency of the MC68HC705SR3CPE?

The MC68HC705SR3CPE supports a maximum crystal frequency of 4 MHz, yielding a 2 MHz bus frequency (E-clock) due to internal divide-by-2. This is confirmed in Section 11.5 "Control Timing" of the Rev. 2.1 datasheet, which specifies timing parameters for both 3 V and 5 V operation at this rate. Higher frequencies risk violating setup/hold times for internal registers and peripherals.

Does the MC68HC705SR3CPE support in-circuit programming?

No, the MC68HC705SR3CPE does not support in-circuit programming. It requires external EPROM programmers applying +12.5 V to the VPP pin (Pin 7) during programming. The device must be removed from the target board and placed in a socketed programmer - verified in Appendix A section A.4.1 "EPROM Programming" and Figure A-1 of the datasheet.

How many analog input channels does the MC68HC705SR3CPE ADC support?

The MC68HC705SR3CPE integrates a 4-channel 8-bit successive-approximation ADC, with inputs mapped to PD0 (AN0), PD1 (AN1), PD2 (AN2), and PD3 (AN3). This is explicitly defined in Table 7-1 "ADC Channel Assignments" and Section 7.1 "ADC Operation", and confirmed in the block diagram (Figure 1-1).

Is the MC68HC705SR3CPE pin-compatible with the MC6805R3?

Yes, the MC68HC705SR3CPE is pin-compatible with the MC6805R3, as stated in the General Description (Section 1): "The MC68HC05SR3 is pin compatible with the MC6805R3 and is provided as a low power upgrade path." This applies to the 40-pin PDIP package (CPE suffix), enabling direct replacement without PCB modification.

What low-power modes are available on the MC68HC705SR3CPE?

The MC68HC705SR3CPE supports three hardware-controlled low-power modes: STOP (CPU and clocks halted, RAM retained), WAIT (CPU halted, clocks active - allows peripheral wake-up), and SLOW (bus frequency reduced to 1/16th normal speed). These are detailed in Section 9 and validated in electrical specs (Section 11.3) showing current draw reductions of >90% in STOP mode.