Data Sheet
Ordering Form
Package Outline
  - DIP-40L
  - QFP-44L
  General Description

The EM78611 is a series of 8-bit Universal Serial Bus RISC architecture microcontroller. It is specifically designed for USB low speed device application and to support standard devices such as PS/2 keyboard. The EM78611 also supports one device address and three endpoints. With no firmware involved, these series of microcontrollers can automatically identify and decode Standard USB Command to Endpoint Zero.
The EM78611 has eight-level stacks and six interrupt sources. It has a maximum of 12 General Input/Output pins. Each device has 144 bytes of general purpose SRAM, and 6K bytes of program ROM. These series of ICs have Dual Clock mode which allows the device to run on very low power saving frequency.

  • Operating voltage 4.4V ~ 5.5
  • Low-cost solution for low-speed USB devices, such as keyboard, joystick, and Gamepad.
  • USB Specification Compliance
    * Universal Serial Bus Specification Version 1.1
    * USB Device Class Definition for Human Interface Device (HID), Firmware Specification Version 1.1
    * Support 1 device address and 3 endpoints
  • USB Application
    * P75(D-) has an internal pull-high resistor ( 1.5K W )
    * USB protocol handling
    * USB device state handling
    * Identifying and decoding of Standard USB commands to EndPoint Zero
  • PS/2 Application Support
    * Built-in PS/2 port interface for keyboard and mouse
  • Built-in 8-bit RISC MCU
    * 8-level stacks for subroutine and interrupt
    * 6 available interrupts
    * 8-bit real time clock/counter (TCC) with overflow interrupt
    * Built-in RC oscillator free running for Watchdog Timer and Dual clock mode
    * Two independent programmable prescalers for WDT and TCC
    * Two methods of saving power:
    -1.) Power-down mode (Sleep mode)
    -2.) Dual clock mode
    * Two clocks per instruction cycle Multi-time programmable
  • I/O Ports
    * Up to 13 LED sink pins
    * Each GPIO pin of Ports 5, 6, 8, and 9; has an internal programmable pull-high resistor ( 25K W )


EM78611E: GPIO pins of Port 5, 6, 8, 9, P76 and P77 are 5Volt I/O.

EM78611: GPIO pins of Port 5, 6, 8, and 9 are 3.3Volt I/O. P76 and P77 are 5Volt I/O.

    * Each GPIO pin of Port 6, P74 ~ P77 and Port 9 can wakeup the MCU from sleep mode by input state change
  • Internal Memory
    * Built-in 6K x 13 bits Program ROM
    * Built-in 144 bytes general purpose registers (SRAM)
    * Built-in USB Application FIFOs
  • Operation Frequency
    * Normal Mode: MCU runs at an external oscillator frequency; 6 MHz or 12 MHz
    * Dual Clock Mode: MCU runs at a frequency of 256 kHz (or 32kHz, 4kHz, 500Hz), emitted by the internal oscillator with the external ceramic resonator turned off to save power.
  • Built-in 3.3V Voltage Regulator
    *Pull-up source for the external USB resistor on D-pin.
  • Package Type:
    * 40-pin PDIP (600mil)                                     EM78611AP
    * 44-pin QFP (10 x 10mm , footprint=3.2mm)  EM78611AQ  
    * 20-pin PDIP (300mil) / SOP (300mil)             EM78611BP/BM  
    * 20-pin SSOP (209mil)                                    EM78611DM
    * 24-pin PDIP (600mil)/SOP (300mil)               EM78611CP/CM
    * 24-pin SSOP (150mil)


  • USB Keyboard only
  • USB and PS/2 both compatible with Keyboard
  • USB Keyboard with USB Mouse
  • USB Joystick