The SI pin is used for serial instruction data input. SI information is latched into the input register on the falling edge of the SCLK. To program a complete word, 32 bits of information must be entered into the device. The SPI logic counts the number of bits clocked into the IC and enables data latching only if exactly 32 bits have been clocked in. In case the word length exceeds or does not meet the required length, the SPI_FAIL bit of the INT_STAT register is asserted to logic 1 and the INT pin will be asserted low. The data received is considered invalid. Note the SPI_FAIL bit is not flagged if SCLK is not present.