Mcu Serial Interface (3-Wire Spi) - Waveshare 13.3 e-Paper (K) User Manual

7.4.3 MCU SERIAL INTERFACE (3-WIRE SPI)

The 3-wire serial interface consists of serial clock SCL, serial data SDA and CS#. This interface
also supports Write mode and Read mode.
The operation is similar to 4-wire serial interface while D/C# pin is not used. There are altogether
9-bits will be shifted into the shift register on every ninth clock in sequence: D/C# bit, D7 to D0 bit.
The D/C# bit (first bit of the sequential data) will determine the following data byte in the shift register
is written to the Display Data RAM (D/C# bit=1) or the command register (D/C# bit=0).
Function
Write command
Write data
In the Read mode:
1. After driving CS# to low, MCU need to define the register to be read.
2. D/C=0 is shifted thru SDA with one rising edge of SCL.
3. SDA is shifted into an 8-bit shift register on every rising edge of SCL in the order of D7, D6, ...
D0.
CS#
L
L
Note: ↑ stands for rising edge of signal
Figure 7-3: Write procedure in 3-wire SPI mode
D/C#
Tie
Tie
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SCL
↑
↑