STMicroelectronics M93S66-WMN6P

Overview

M93S66-WMN6P from STMicroelectronics is a 4 Kbit (256 × 16-bit) serial EEPROM with MICROWIRE bus interface, user-configurable write protection, and OTP-locked protection register. It operates from 2.5 V to 5.5 V, supports 2 MHz clock, delivers ≤5 ms page write time, and guarantees >4 million write cycles and >200-year data retention over –40 °C to +85 °C. Used in industrial control modules for storing calibration coefficients and configuration settings.

For engineers reviewing the M93S66-WMN6P datasheet, M93S66-WMN6P pinout, M93S66-WMN6P application, or M93S66-WMN6P equivalent, key selection criteria include write-protection granularity, MICROWIRE timing compliance, SO8 package footprint compatibility, and guaranteed endurance at extended temperature.

Technical Context

The M93S66-WMN6P implements a synchronous serial MICROWIRE interface with start-bit–driven instruction framing and on-chip clock-pulse counter for noise immunity. All instructions (READ, WRITE, PAWRITE, WRAL, PRREAD, PRWRITE, PREN, etc.) require precise bit-count alignment-e.g., WRITE requires exactly 27 clock pulses from start bit to S falling edge-to prevent misaligned writes.

Memory is organized as 256 words of 16 bits each, with page size = 4 words (64 bits). Write protection is controlled via an 8-bit Protection Register (PR) and enforced by the W input signal; permanent lock is achieved by programming the OTP bit during PRDS instruction, disabling further PR modification.

Key Specifications

Pinout & Package

Package: SO8 (MN), 8-lead plastic small outline, 150 mil body width, ECOPACK®2 compliant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with AT25040B-MAU-1.8 and BR24G04FJ-WE2, the M93S66-WMN6P uniquely combines MICROWIRE timing robustness, user-defined protected zones, and OTP-enforced PR immutability-critical for industrial safety-critical configuration storage.

Availability

M93S66-WMN6P is available at Aetrix Electronics and suitable for industrial sensor calibration, PLC configuration storage, and motor drive firmware settings requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for M93S66-WMN6P 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, specializing in microcontrollers, power management, sensors, and nonvolatile memory solutions for industrial, automotive, and consumer markets.

The M93S66-W series belongs to ST's legacy serial EEPROM product line, designed specifically for robust, low-pin-count, noise-immune configuration storage in harsh industrial environments where MICROWIRE compatibility and hardware-enforced write protection are mandatory.

FAQ

What is the function of the PRE pin on the M93S66-WMN6P?

The PRE (Protection Register Enable) pin must be driven high to access the Protection Register (PR) for reading, writing, or clearing. It acts as a hardware gate-PR operations (PRREAD, PRWRITE, PRCLEAR, PREN, PRDS) are ignored unless PRE is asserted high during the instruction sequence. This prevents accidental modification of write protection settings during normal memory access.

Can the M93S66-WMN6P be used with a 3.3 V microcontroller without level shifting?

Yes. The M93S66-WMN6P operates from 2.5 V to 5.5 V and has VIH(min) = 0.7×VCC and VIL(max) = 0.3×VCC. At VCC = 3.3 V, VIH(min) = 2.31 V and VIL(max) = 0.99 V, making it fully compatible with standard 3.3 V CMOS logic levels-no level shifter required for S, C, D, PRE, or W signals.

How does the clock-pulse counter prevent corrupted writes in noisy environments?

The on-chip counter validates the exact number of clock pulses received between the start bit and the falling edge of S. For example, a WRITE instruction requires precisely 27 pulses. If noise adds or drops a pulse-causing misalignment-the instruction is aborted and memory contents remain unchanged. This eliminates silent data corruption from EMI or signal integrity issues on the C line.

Is the OTP bit in the M93S66-WMN6P reversible once programmed?

No. The One-Time Programming (OTP) bit is set permanently by executing the PRDS (Protection Register Disable) instruction. Once set, the Protection Register becomes read-only and cannot be rewritten, cleared, or re-enabled-even with power cycling or VCC reset. This provides irreversible hardware-enforced security for critical configuration data.