MC144032B6WCB-SPTLY Midas, MC144032B6WCB-SPTLY Datasheet - Page 15

• Manufacturer Part Number: MC144032B6WCB-SPTLY
• Description: LCD, 144X32, STN, Y/GN B/L, CHINESE; Backlighting Colour: Yellow Green; LCD Display Type: STN; Pixel Size (H x W): 0....
• Manufacturer: Midas

Serial interface :
ST7920 is in serial interface mode when pull down PSB pin. Two pins (SCLK and SID) are used
to complete the data transfer. Only write data is available.
When connecting several ST7920, chip select (CS) must be used. Only when (CS) is high the
serial clock (SCLK) can be accepted. On the other hand, when chip select (CS) is low ST7920
serial counter and data will be reset. Transmission will be terminated and data will be cleared.
Serial transfer counter is set to the first bit. For a minimal system with only one ST7920 and one
MPU,
only SCLK and SID pins are necessary. CS pin should pull to high.
ST7920’s serial clock SCLK is asynchronous to the internal clock and is generated by MPU.
When multiple instruction/data is transferred instruction execution time must be considered.
Must wait for the previous instruction to finish before sending the next. ST7920 has no internal
instruction buffer area.
When starting a transmission a start byte is required. It consists of 5 consecutive ”1”(sync
character). Serial transfer counter will be reset and synchronized. Following 2 bits for read/write
(RW) and register/data select (RS). Last 4 bits is filled by “0”
After receiving the sync character and RW and RS bits, every 8 bits instruction/data will be
separated into 2 groups. Higher 4 bits (DB7~DB4) will be placed in first section followed by 4 “0”.
And lower 4 bits DB3~DB0 will be placed in second section followed by 4 “0”.
Timing Diagram of Serial Mode Data Transfer