STE2004 datasheet(30/66 Pages) STMICROELECTRONICS

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STE2004

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Figure 37. 4-lines SPI Reading Sequence

4.2.2 3-lines SPI Interface

The STE2004 3-lines serial Interface is a bidirectional link between the display driver and the application

supervisor.

It consists of three lines: one/two for data signals (SDIN,SDOUT), one for clock signals (SCLK) and one

for peripheral enable (CS).

If the R/W bit is set to logic 0 the STE2004 is set to be a receiver. One or more command word follows to

define the status of the device.

A command word is composed by two bytes. The first is a control byte which defines Co, D/C, R/W H[1;0]

and HE values, the second is a data byte (fig 39). The Co bit is the command MSB and defines if after this

command will follow one data byte and an other command word or if will follow a stream of Commands or

a Steam of DDRAM Data (Co = 1 Command word, Co = 0 Stream of data). The D/C bit defines whether

the data byte is a command or DDRAM data (D/C = 1 RAM Data, D/C = 0 Command). The H[1;0] bits

define the instruction Set Page if HE bit =1. If HE bit is set to 0 H[1;0] values are neglected and it is possible

to update the instruction set page number using only the related instruction in the instruction Set.

If Co =1 and D/C = 0 the incoming data byte is decoded as a command, and if Co =1 and D/C =1, the

following data byte will be stored in the data RAM at the location specified by the data pointer.

After the last control byte, if D/C is set to a logic 1 the incoming data bytes are stored inside the STE2004

Display Data RAM starting at the address specified by the data pointer. The data pointer is automatically

updated after every byte written and in the end points to the last RAM location written.

Throughout SDOUT can be read the driver I2C slave address or the status Byte. The Command sequence

that allows to read I2C slave address or the Status byte is reported in Fig. 39 & 40.

If the R bit is set to logic 0 and D/C=0, the I2C slave address is read; If the R bit is set to logic 1 and D/

C=0, the the I2C slave address is read

SDOUT is in High impedance in steady state and during data write.

It is possible to short circuit SDOUT and SDIN and read I2C address or status byte without any additional

line.

READING SEQUENCE

Write a "00000000" Instruction

Source 8 pulses on SCLK and

Read the ID Number or the Status Byte On SDOUT

END OF READING SEQUENCE

SDOUT Buffer Configured in High Impedence

LR0078

SDOUT Buffer becomes active (Low Impedence)

note: 1) these data are not read by the display Diver

2) SDIN and SDOUT can be short circuited if the processor can configure

serial output buffers in high impedence during data read

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