20.5.2.1.1 IWCOL Status Flag

If the user software writes to the I2CxTRN register when a Start sequence is in progress, the IWCOL status bit (I2CxSTAT1[7]) is set and the contents of the transmit buffer are unchanged (the write does not occur).

Note: As the queuing of events is not allowed, writing to the lower five bits of the I2CxCON1 register is disabled until the Start condition is complete.

Figure 20-7. Host Start Timing Diagram