  We developed and built a new system of readout and trigger electronics, based
on the waveform digitization and pipeline readout, for the KOTO experiment at
J-PARC, Japan. KOTO aims at observing the rare kaon decay
$K_{L}\rightarrow\pi^{0}\nu\bar{\nu}$. A total of 4000 readout channels from
various detector subsystems are digitized by 14-bit 125-MHz ADC modules
equipped with a 10-pole Bessel filter in order to reduce the pile-up effects.
The trigger decision is made every 8-ns using the digitized waveform
information. To avoid dead time, the ADC and trigger modules have pipelines in
their FPGA chips to store data while waiting for the trigger decision. The KOTO
experiment performed the first physics run in May 2013. The data acquisition
system worked stably during the run.
