SPRUJ53B April 2024 – September 2024 TMS320F28P550SJ , TMS320F28P559SJ-Q1
Every time there is a soft reset of the receiver, the receiver requires a flush sequence from the transmitter before the receiver can receive and decode frames. The receiver core has an asynchronous reset mechanism that allows the receive module to be reset even in the absence of the receive clocks. However, due to the design, this reset is released synchronous to the receive clock (RXCLK). Thus, the receiver requires five full clock pulses to be able to come out of reset. Sending the flush pattern makes sure that these clock edges are received and any subsequent frames sent to the receiver are correctly interpreted.
The flush sequence consists of a single toggle on both of the data lines as well as five consecutive pulses on the clock line.
If the FSI receiver is receiving data from a standard SPI, a data word of 0xFFFF from the SPI has the same effect as a flush sequence.
Figure 25-8 shows a sample plot of the flush sequence.