long padding phase with ISM43362 on a BL475 discovery board

Dear all,

I wrote a 'WIFI Terminal' program that bridges between a terminal program on my PC and the ISM43362 WIFI module on my BL475 discovery board.
So far it looks everything OK concerning the functionality. However, I'm surprised about the long padding phase in 'data receive mode'. So everytime the ISM43362 is answering to a command I send it takes about 300usec between its dataready signal and meaningful data output. Within this 300usec the ISM43362 is sending padding data. This padding data is documented in the ISM43362 specification. But in this specification it only talks about 2 padding bytes (which is true for the first response after reset).
In the screenshot you can see a communication cycle. Around -300usec the command is send to the ISM43362. Just after -300usec it is answering with the dataready signal. 'Meaningful' data is not send before 0usec. The fast follwing red SPI blocks you see are blocks were I receive the padding characters (each block = 16bit). After 0usec you can see that I receive a 16Bit block via SPI that I transmit with two 8Bit blocks via USART back to the PC terminal program. All time consuming blocks you see in the screenshot are running in ISR to be as fast as possible.
Anybody has similar experience?
Best Regards
Markus