  An experiment that measured the parity-violating asymmetries in deep
inelastic scattering was completed at the Thomas Jefferson National Accelerator
Facility in experimental Hall A. From these asymmetries, a combination of the
quark weak axial charge could be extracted with a factor of five improvement in
precision over world data. To achieve this, asymmetries at the $10^{-4}$ level
needed to be measured at event rates up to 600 kHz and the high pion background
typical to deep inelastic scattering experiments needed to be rejected
efficiently. A specialized data acquisition (DAQ) system with intrinsic
particle identification (PID) was successfully developed and used: The pion
contamination in the electron samples was controlled at the order of $2\times
10^{-4}$ or below with an electron efficiency of higher than 91 % during most
of the production period of the experiment, the systematic uncertainty in the
measured asymmetry due to DAQ deadtime was below 0.5 %, and the statistical
quality of the asymmetry measurement agreed with the Gaussian distribution to
over five orders of magnitudes. The DAQ system is presented here with an
emphasis on its design scheme, the achieved PID performance, deadtime effect
and the capability of measuring small asymmetries.
