The W78LE812 is an 8-bit microcontroller which can accommodate a wide range of supply voltages with low power consumption. The instruction set for the W78LE812 is fully compatible with the standard 8051. The W78LE812 contains an 8K bytes MTP ROM (Multiple-Time Programmable ROM); a 256 bytes RAM; four 8-bit bi-directional and bit-addressable I/O ports; an additional 6-bit I/O port P4; three 16-bit timer/counters; a hardware watchdog timer and a serial port. These peripherals are supported by a fourteen sources two-level interrupt capability. To facilitate programming and verification, the MTP-ROM inside the W78LE812 allows the program memory to be programmed and read electronically. Once the code is confirmed, the user can protect the code for security. The W78LE812 microcontroller has two power reduction modes, idle mode and power-down mode, both of which are software selectable. The idle mode turns off the processor clock but allows for continued peripheral operation. The power-down mode stops the crystal oscillator for minimum power consumption. The external clock can be stopped at any time and in any state without affecting the processor.