The ADS1291, ADS1292, and ADS1292R serial interface decodes commands in bytes and requires 4 tCLK cycles to decode and execute. Therefore, when sending multi-byte commands, a 4 tCLK period must separate the end of one byte (or opcode) and the next.
Assume CLK is 512 kHz, then tSDECODE (4 tCLK) is 7.8125 µs. When SCLK is 16 MHz, one byte can be transferred in 500 ns. This byte-transfer time does not meet the tSDECODE specification; therefore, a delay must be inserted so the end of the second byte arrives 7.3125 µs later. If SCLK is 1 MHz, one byte is transferred in 8 µs. Because this transfer time exceeds the tSDECODE specification, the processor can send subsequent bytes without delay. In this later scenario, the serial port can be programmed to move from single-byte transfer per cycle to multiple bytes.