Raghunathan,

SPI is described in a fair number of Motorola microprocessor data sheets, particularly the 68HC11 series. In addition, Microchip's PIC18F458 datasheet, pages 143 through 151 discuss SPI operation within the context of the PIC's Master Synchronous Serial Port. Table 17-1 on page 151 identify standard identifiers for four modes of operation.

Keep in mind the SPI is much like RS232, RS485, etc. in that it describes a hardware protocol (which happens to transmit eight bits per frame). You may choose clock edges to transfer data in and out of the master and slave as well as the idle state of the clock.

Bruce