STMicroelectronics Announces New Supervisors Providing Additional Protection Should Power Fail.

Business & Technology Editors

GENEVA--(BUSINESS WIRE)--Sept. 26, 2001

Two serial real-time clock chips integrate many supervisory

functions including early power-fail warning providing the

ultimate protection against lost data

STMicroelectronics (NYSE: STM) has announced two full-featured microprocessor supervisor chips, each bearing a serial real-time clock, internal write-protect circuitry, and a power supply monitor that provides early warning of a power failure, thereby leaving time to save key data and initiate a graceful shutdown.

The M41ST84 and M41ST85 each come in 3V and 5V versions and will find ready demand from applications such as arcade and other computer games, medical systems, servers, point-of-sale terminals, SCSI peripherals and vending machines. Available functions include a nonvolatile time-of-day clock/calendar, alarm interrupts, watchdog timer, and square wave output. The reset output provides power-on reset and a low-voltage reset.

The M41ST84 built-in power sense circuit detects power failures and automatically switches to battery power, which sustains the real-time clock and SRAM. The early power-fail warning circuit, which contains a 1.25V precision reference and comparator, can alternatively be used to monitor a secondary supply in multiple voltage systems.

The M41ST84 is organized as 64 bytes with 20 registers and 44 bytes of NVRAM. A built-in 32.768kHz oscillator drives the real-time clock, which is accessed via eight registers, which provide clock and calendar information in binary-coded decimal format. Specifically, the eight clock addresses store century, year, month, date, day, hour, minute, second, and tenths/hundredths of a second. Corrections for leap years (through year 2100) and 30- and 31-day months are automatic. A ninth register controls user access to the clock information and stores the clock calibration setting.

Another 11 locations are devoted to alarm, watchdog, and square-wave functions. Address and data move serially across a bidirectional 400kHz I2C bus, and a built-in address register increments automatically after a byte is read or written thereby allowing burst accesses.

The companion M41ST85 Serial RTC/NVRAM SUPERVISOR combines all the features of the M41ST84 with a nonvolatile RAM supervisor. The supervisor includes battery switchover and write-protect circuits that supply power and chip-enable gating to an external low-power SRAM, thereby making it non-volatile. The M41ST85 also includes a debounced input for generating a push-button reset output.

Both the M41ST84 and the M41ST85 draw a maximum of 500nA of battery current and only 400uA of supply current when active. The M41ST84 is available in a 16-pin SOIC package while the M41ST85 comes in the SNAPHAT(R) 28-pin SOIC package for use with ST's removable SNAPHAT top. The SNAPHAT top contains a lithium battery and 32kHz crystal and can be easily replaced when necessary, typically after 10 years.

The -Y versions of the M41ST84 and M41ST85 supervisor chips operate at supply voltages between 4.5V and 5.5V, and deselect at 4.4V +/-0.10V; -W versions operate at supply voltages between 2.7V and 3.6V and deselect at 2.625V +/-0.075V. All operate over the industrial (-40 to 85(degree)C) temperature range. Sample units are available now from local distributors.

About STMicroelectronics

STMicroelectronics is the world's third largest independent semiconductor company. The Company shares are traded on the New York Stock Exchange, on Euronext Paris and on the Milan Stock Exchange. The Company designs, develops, manufactures and markets a broad range of semiconductor integrated circuits (ICs) and discrete devices used in a wide variety of microelectronic applications, including telecommunications systems, computer systems, consumer products, automotive products and industrial automation and control systems. In 2000, the Company's net revenues were $7,813.2 million and net earnings were $1,452.1 million. Further information on ST can be found at www.st.com.