GENERAL DESCRIPTION
The MTU420 is an LCD driver with an embedded high-performance 4-bit microcomputer. It contains all the necessary functions in a single chip: dual clock, 4-bit parallel processing ALU, ROM, RAM, input/output ports, timer, clock generator, LCD driver, look-up table and watchdog timer. The set of 118 instructions includes not only 4-bit operation and manipulation instruction but also various conditional branch instructions, and LCD driver data transfer instructions that are powerful and easy to follow. The halt function stops internal operations other than the oscillator, divider and LCD driver in order to minimize power dissipation. The stop function stops all clocks in the chip.

FEATURES
• Wide operating voltage range:
• 118 instruction sets:
   - Binary addition, subtraction, BCD adjustment, logical operation in direct addressing mode and index addressing mode.
   - Single-bit manipulation (set, reset, decision for branch).
   - 4-bit input/output.
   - Various conditional branches.
   - 16 working registers and manipulation.
   - LCD driver data transfer.
   - Look-up table.
   - Programmable option.
   - System clock selection.
• 8-level subroutine nesting.
• Interrupt function:
   - External factor: 2 (INT pin or ports S, M).
   - Internal factor: 2 (timer, divider).
• ROM/RAM capacity:
   - ROM capacity . . . . . 2048 x 16 bits.
   - RAM capacity . . . . . 128 x 4 bits.
• Watchdog timer.
• Input/Output ports:
   - Input ports . . . . . 2 ports/8pins (S, M).
   - Output port . . . . . 1 port/4pins (P).
   - Pseudo serial output port . . . . . Also used for output port.
   - Input/Output ports . . . . . 2 ports/8pins (I/OA, I/OB).
• 2 control outputs . . . . . light, alarm.
• LCD driver output:
   - 26 LCD driver outputs (up to 156 LCD segments are drivable).
   - Mask option is used to select static ½ duty, ½ bias ½ duty, ½ bias 1/3 duty, ½ bias ¼ duty, 1/3 bias 1/3 duty, ½ bias ¼ duty and 1/3 bias 1/6 duty drive modes of the LCD panel.
   - Mask option permits LCD driver output pins to be used for output ports.
   - Segment PLA circuit permits any layout on the LCD panel.
• Built-in doubler, halver, tripler.
• One 6-bit timer with programmable option clock.
• 128-byte look-up table for LCD display pattern or 256-nibble look-up table for general purpose.
• Halt function.
• Stop function.
• Dual clock operation.