  The VMM3a is an Application Specific Integrated Circuit (ASIC), specifically
developed for the readout of gaseous detectors. Originally developed within the
ATLAS New Small Wheel (NSW) upgrade, it has been successfully integrated into
the Scalable Readout System (SRS) of the RD51 collaboration. This allows, to
use the VMM3a also in small laboratory set-ups and mid-scale experiments, which
make use of Micro-Pattern Gaseous Detectors (MPGDs). As part of the integration
of the VMM3a into the SRS, the readout and data transfer scheme was optimised
to reach a high rate-capability of the entire readout system and profit from
the VMM3a's high single-channel rate-capability of 3.6 Mhits/s. The
optimisation focused mainly on the handling of the data output stream of the
VMM3a, but also on the development of a trigger-logic between the front-end
cards and the DAQ computer. In this article, two firmware implementations of
the non-ATLAS continuous readout mode are presented, as well as the
implementation of the trigger-logic. Afterwards, a short overview on X-ray
imaging results is presented, to illustrate the high rate-capability rom an
application point-of-view.
