EM6625- With LCD Driver

OBSOLETE PRODUCT - replaced by EM6627 - Ultra-Low Power

Ultra-low power Microcontroller with 4x20 LCD driver

General Description

The EM6625 is an advanced single chip, low cost CMOS 4-bit microcontroller. It contains ROM, RAM, LCD driver, power on reset, watchdog timer, oscillation detection circuit, 10-bit up/down and event counter, 1ms BCD counter, prescaler, voltage level detector (Vld), serial interface and several clock functions. The low voltage feature and low power consumption make it the most suitable controller for battery, stand alone and mobile equipment. The EM6625 is manufactured using an Advanced Low Power CMOS process. The EM6625 is an improved version of EM6621, with additional features such as 32/128 kHz crystal oscillator and 32/42.7/64 Hz LCD frequency for optimal use in communication applications.


  • Household appliances
  • Timer/sports timing devices
  • Bicycle computers
  • Measurement equipment
  • Security, safety systems
  • Medical devices
  • Interactive systems with display

Buzzer on the emulator EM6621/22/25/26 and EM6821
The Emulator Buzzer output connector pin (nbr 21) does only pull high and its tristate function is not correctly implemented.
Correction: New emulators dated march/2000 and up are ok. The old emulators need to be send back to EM for correction, or EM should send a corrected FPGA setup EEPROM.

Emulator Bug
The instructions NAND, NANDS, NANDX, NANDXS do not work on the emulator.
They are working correctly on simulator and chip.
Valid for all members of the 4-bit microcontroller family.

Demo Programs
Example program for the EM6621/25: This program implements a simple clock, with an alarm.

Example program for the demo board EM6521: Mastermind

Ohmmeter by the measurement of resistors

Example program on EM microcontroller peripherals

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  • Low Power - 1.6 µA active mode, LCD On
    • - 0.4 µA standby mode, LCD Off
    • - 0.2 µA sleep mode
    • @ 3V , 32 KHz, 25 ºC
  • True Low Voltage - 1.2 to 3.6 V
  • 32kHz/128kHz crystal oscillator
  • LCD frequency 32Hz/42.7Hz/64Hz
  • 2 clocks per instruction cycle
  • RISC architecture (72 basic instructions)
  • ROM 4096 x 16 (Mask Programmed)
  • RAM 128 x 4 (User Read/Write)
  • Max. 12 inputs ; port A, port B, port SP
  • Max. 8 outputs ; port B, port SP
  • Voltage Level Detector, 8 levels software selectable from 1.2 V up to 4.0 V
  • Melody, 7 tones + silence inclusive 4-bit timer
  • Universal 10-bit counter, PWM, event counter
  • Prescaler down to 1 second ( crystal = 32 KHz )
  • 1/1000 sec 12 bit binary coded decimal counter with hard or software start/stop function
  • LCD 20 Segments, 3 or 4 times multiplexed
  • 3 wire serial port , 8 bit, master and slave mode
  • 5 external interrupts (port A, serial interface)
  • 8 internal interrupts (3x prescaler, BCD counter, 2x10-bit counter, melody timer, serial interface)
  • Timer watchdog and oscillation supervisor
  • Equivalent MFP version available (EM6521)