The TTCrx monitor card is read out through PCI by single access. This limits the DAQ column event rate to about 15.5 kHz. A faster access bypassing the HAL is easy to implement, while a really fast access by DMA is more complicated. Ocassional errors were observed in reading the TTCrx, possibly due to an old FPGA version.
A NIM trigger generator logic is set up, with uniform rate and backpressure from either the TTCrx monitor or the fedkit card. In case of random rate the backpressure can not be applied, would be possible using two TTCvi cards.