I would use a digital controller. This can either be on chip or off-chip. In various projects, I have used Xilinx FPGA, National Instrument PXIe cards (6570 or 6571 are really good), Arduino, Raspberry Pi, and even on-chip controllers to generate pulses on-demand. If it’s your first project and you are unfamiliar, I recommend using something simple like Raspberry Pi or Arduino. This will not be able to generate very fast pulses though. If you want to do that, you should upgrade to FPGA or other fast pulse generator or integrate on-chip controller circuit before you tapeout