CS5378 datasheet(45/86 Pages) CIRRUS

45 / 86 page

CS5378

DS639F1

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 CS5378 FIR filter performs dou-

ble 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 27 or “Microcontroller Configuration Com-

mands” on page 33 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.

CS5378 データシート(PDF) 45 Page - Cirrus Logic