Piccolo LED Controller hosts a 4-wire SPI slave interface that serves as the communication port to the display controller. The SPI interface supports high-speed serial data transfers up to 400 kHz. Following four pins are used for SPI communication:

• SPISOMI:SPI slave-output/master-input pin
• SPISIMO:SPI slave-input/master-output pin
• SPISTEn:SPI slave transmit-enable pin
• SPICLK:SPI serial-clock pin

The SPISTEn pin operates as the slave-select pin. A high (inactive) signal causes the slave SPI serial shift register to stop and its serial output pin to be put into the high-impedance state. The SPISIMO input serves as the serial data input for the port (from the master to Piccolo); the SPISOMI output serves as the serial data output (from Piccolo to master).

The SPICLK input serves as the serial data clock for both the input and output data. Data is latched at the SPISIMO input on the rising edge of SPICLK, while data is clocked out of the SPISOMI output on the falling edge of SPICLK.

The following diagram shows an outline of connection between Piccolo (SPI Slave) and Display Controller (SPI Master).

Figure 1-1 Block Diagram