  Due to the periodic characteristics of SQUIDs, a suitable linearization
technique is required for SQUID-based readout. Flux-ramp modulation is a common
linearization technique and is typically applied for the readout of a
microwave-SQUID-multiplexer as well as since recently also for dc-SQUIDs.
Flux-ramp modulation requires another stage in the signal processing chain to
demodulate the SQUID output signal before further processing. For cryogenic
microcalorimenters, these events are given by fast exponentially rising and
slowly exponentially decaying pulses which shall be detected by a trigger
engine and recorded by a storage logic. Since the data rate can be decreased
significantly by demodulation and event detection, it is desirable to do both
steps on the deployed fast FPGA logic during measurement before passing the
data to a general-purpose processor.
  In this contribution, we show the implementation of efficient multi-channel
flux-ramp demodulation computed at run-time on a SoC-FPGA. Furthermore, a
concept and implementation for an online trigger and buffer mechanism with its
theoretical trigger loss rates depending on buffer size is presented. Both FPGA
modules can be operated with up to 500 MHz clock frequency and can efficiently
process 32 channels. Correct functionality and data reduction capability of the
modules are demonstrated in measurements utilizing magnetic microcalorimeter
irradiated with an Iron-55 source for event generation and read out by a
microwave SQUID multiplexer.
