INTRODUCTION
The ST7556 is a driver & controller LSI for graphic dot-matrix liquid crystal display systems. It contains 102 segment and 65 common with 1 ICOM driver circuits. This chip is connected directly to a microprocessor, accepts 4-line serial interface (SPI) or 8-bit parallel interface, display data can store in an on-chip display data RAM of 66 x 102 bits. It performs display data RAM read/write operation with no external operating clock to minimize power consumption. In addition, because it contains power supply circuits to drive liquid crystal, it is possible to make a display system with the fewest components.

FEATURES
Driver Output Circuits
102 segment outputs / 65+1 common outputs
On-chip Display Data ram
  - Capacity: 66X102=6,732 bits Microprocessor Interface
  - 8-bit parallel bi-directional interface with 6800-series or 8080-series
  - 4-line SPI (serial peripheral interface) available (only write operation)
On-chip Low Power Analog Circuit
  - Generation of LCD supply voltage (externally Vout voltage supply is possible)
  - Generation of intermediate LCD bias voltages
  - Oscillator requires no external components (external clock also possible)
  - Voltage converter (x4)
  - Voltage regulator (temperature gradient -0.05%/°C)
  - Voltage follower
  - On-chip electronic contrast control function (128 steps)
  - Liquid crystal driving voltage : V0 -VSS = max 12 V (external power supply)
External RESB (reset) pin
Logic supply voltage range VDD -VSS
  - 1.8 to 3.3V
Temperature range: -30 to +85 degree