Cirrus Logic CS5376A - Manual (Page 48)

CS5376A
48 DS612F4
13.4 Programmable FIR Coefficients
A maximum of 255 + 255 coefficients can be pro-
grammed into FIR1 and FIR2 to create a custom
filter response. The total number of coefficients for
the FIR filter is fundamentally limited by the avail-
able computation cycles in the digital filter, which
itself is determined by the digital filter clock rate.
Custom filter sets should normalize the maximum
coefficient value to 24-bit two’s complement full
scale, 0x7FFFFF, and scale all other coefficients
accordingly. To maintain maximum internal dy-
namic range, the CS5376A FIR filter performs
double precision calculations with an automatic
gain correction to scale the final output.
Custom FIR coefficients are uploaded using the
‘Write FIR Coefficients’ configuration command.
See “EEPROM Configuration Commands” on
page 28 or “Microcontroller Configuration Com-
mands” on page 35 for information about writing
custom FIR coefficients.
13.5 FIR Filter Synchronization
The FIR1 and FIR2 filters are synchronized to the
external system by the MSYNC signal, which is
generated from the SYNC input. The MSYNC sig-
nal sets a reference time (time 0) for all filter oper-
ations, and the FIR filters are restarted to phase
align with this reference time.