ADLINK PCI-7300A - Manual (Page 52)

40 Operation Theory
4.8 Starting Mode
Users can also control the starting mode of digital input and output
by external signals (DITRIG and DOTRIG) with the software pro-
grams. The trigger modes includes NoWait, WaitTRIG, WaitFIFO,
and WaitBoth.
1. NoWait: The data transfer is started immediately when a
I/O transfer command is issued.
2. WaitTRIG: The data transfer will not start until external
trigger signal (DI-TRIG for digital input, DO-TRIG for dig-
ital output) is activated.
3. WaitFIFO: This starting mode is only available for digital
output. The data transfer is started until the output FIFO
is not almost empty. The threshold of FIFO almost empty
is software programmable.
4. WaitBoth: This starting mode is only available for digital
output. The data transfer is started until the output FIFO
is not almost empty and DO-TRIG signal is activated.
The software driver functions of 5.6 and 5.7 are provided to setup
the starting mode of digital input and digital output, respectively.
4.9 Active Terminator
For cPCI/PCI-7300A, it is important to terminate your cable prop-
erly to reduce or eliminate signal reflections in the cable. The PCI-
7300A support active terminator on board, you can enable or dis-
able the terminator by software selection (Please refer to section
5.5 function _7300_config).
The active terminator is the same as the one used in SCSI 2.
When the terminator is ON, it presents a terminal 110-ohm imped-
ance to the transmission line to match the line impedance. When it
is OFF, it just add a few pF capacitance to the line