ADLINK cPCI-7300 - Manual (Page 41)

Operation Theory • 33
2. WaitTRIG: The data transfer will not start until external trigger signal
(DI-TRIG for digital input, DO-TRIG for digital 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 properly to reduce
or eliminate signal reflections in the cable. The PCI-7300A support active
terminator on board, you can enable or disable 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 impedance to the
transmission line to match the line impedance. When it is OFF, it just add a few
pF capacitance to the line
4.10 Digital Input Operation Mode
4.10.1 Digital Input DMA in Internal Clock Mode
There are three sources to trigger digital input in the internal clock mode:
20MHz, 10MHz, and programmable timer 82C54. There are three counters in
82C54, where the counter 0 is used for sampling clock source for digital input.
The operations sequence of digital input with internal clock are listed as
follows:
1. Define the input configuration to be 32-bit, 16-bit or 8-bit data width.
2. Enable or disable the active terminators.
3. Define the input sampling rate to be 20MHz, 10MHz, or the output of 82C54
counter 0.