ADLINK PCIe-7300A - Manual (Page 113)

Appendix 103
Mode 5: Hardware Triggered Strobe.
The counter will start counting after the rising edge of the trig-
ger input and will go low for one clock period when the terminal
count is reached. The counter is re-triggerable. the output will
not go low until the full count after the rising edge of any trigger.
The detailed description of the 8254, please refer to the Intel
Microsystem Components Handbook.