ks0074 Samsung Semiconductor, Inc., ks0074 Datasheet - Page 45

• Manufacturer Part Number: ks0074
• Description: 34com/80seg Driver & Controller For Dot Matrix Lcd
• Manufacturer: Samsung Semiconductor, Inc.

KS0074
34COM/80SEG DRIVER & CONTROLLER FOR DOT MATRIX LCD
Interface with MPU in Serial Mode
When IM port input is "Low", serial interface mode is started. At this time, all three ports,
SCLK (synchronizing transfer clock), SID (serial input data), and SOD (serial output data), are used. If KS0074 is to be
used with other chips, chip select port (CS) be used.
By setting CS to "Low", KS0074 can receive SCLK input. If CS is set to "High", KS0074 reset the internal transfer counter.
Before transfer real data, start byte has to be transferred. It is composed of succeeding 5 "High" bits, read write
control bit (R/W), register selection bit (RS), and end bit that indicates the end of start byte. Whenever succeeding
5 "High" bits are detected by KS0074, it resets serial transfer counter and prepares to receive next information.
The next input data are register selection bit which determine which register is to be used, and read write control bit
that determine the direction of data. Then end bit is transferred, which must have "Low" value to show the end of
start byte. (Refer to Fig 13. Fig 14)
(1) Write Operation (R/W = 0)
After start byte is transferred from MPU to KS0074, 8-bit data is transferred which is divided into 2 bytes, each byte
has 4 bit's real data and 4 bit's partition token data. For example, if real data is "10110001" (D0 - D7), then serially
transferred data becomes "1011 0000 0001 0000" where 2nd and 4th 4 bits must be "0000" for safe transfer.
To transfer several bytes continuously without changing R/W bit and RS bit, start byte transfer is needed only at first
starting time. I.e., after first start byte is transferred, real data succeeding can be transferred.
(2) Read Operation (R/W = 1)
After start byte is transferred to KS0074, MPU can receive 8-bit data through the SOD port at a time from the LSB.
Wait time is needed to insert between start byte and data reading, as internal reading from RAM requires some delay.
Continuous data reading is possible such as serial write operation. It also needs only one start bytes, only if some
delay between reading operations of each byte is inserted. During the reading operation, KS0074 observes
succeeding 5 "High" from MPU. If detected, KS0074 restarts serial operation at once and prepares to receive RS bit.
So in continuous reading operation, SID port must be “Low”.