SLASEG6B May 2018 – June 2020 TAS3251
The swap flag is used to copy the audio coefficient from the host memory to the DSP memory. The swap flag feature is important to maintain the stability of the BQs. A BQ is a closed-loop system with 5 coefficients. To avoid instability in the BQ in an update transition between two different filters, update all five parameters within one audio sample. The interal swap flag insures all 5 coefficients for each filter are transferred from host memory to DSP memory occurs within an audio sample. The swap flag stays high until the full host buffer is transferred to DSP memory. Updates to the Host buffer should not be made while the swap flag is high.
All writes to book 0x8C at pages above page 0x1B and register 0x58 require the swap flag. The swap flag is located in book 0x8C, page 0x05page 0x01, and register 0x7C and must be set to 0x00 00 00 01 for a swap.