Instruction manual

AMPDIO DRIVERS
Page 50
occurring at the start of every buffer. It is recommended that the hardware fix is applied to avoid the
problem altogether.
3.4.3.2.1.2 Controlling Start of Aquisition on PCI230+ and PCI260+
For the new PCI230+ and PCI260+ cards, it is possible to delay the start of acquisition until a
programmable start acquisition trigger occurs. Alternatively, data can be acquired as normal while
keeping a count of the number of samples stored until the start acquisition trigger occurs. If the
card is set to delay the start of acquisition, data acquired from each channel will be placed into a
temporary buffer instead of the FIFO, and then either discarded (if the trigger has not occurred yet)
or transferred to the FIFO (if the trigger has occurred). Once the start acquisition trigger has
occurred, subsequent channel readings will be placed into the FIFO as normal.
The function AIOsetADCstartAcquisitionTrigger (see section 6.4.19.5) is used to set the start
acquisition trigger. This is supported since version 4.42 of the AMPDIO driver and DIO_TC.DLL.
The following start acquisition trigger types are supported by PCI230+ and PCI260+ cards:
TRIG_NOW Trigger immediately.
TRIG_NEVER Never trigger.
TRIG_EXT_LTOH Trigger on external digital low-high transition.
TRIG_EXT_HTOL Trigger on external digital high-low transition.
TRIG_EXT_LOW Trigger when external digital signal is low.
TRIG_EXT_HIGH Trigger when external digital signal is high.
TRIG_ANA_LTOH Trigger on analogue low-high transition.
TRIG_ANA_HTOL Trigger on analogue high-low transition.
TRIG_ANA_LOW Trigger when analogue value is low.
TRIG_ANA_HIGH Trigger when analogue value is high.
For start acquisition triggers involving an analogue value, the channel, threshold, hysteresis and a
hold-off value are specified in the function call. (The hysteresis is applied for ‘TRIG_ANA_LTOH’
and ‘TRIG_ANA_HTOL’.) The specified channel should be one of those being acquired by the user
interrupt, as no other channels will be sampled. It should also be noted that analogue levels and
transitions are only detected when it is the specified channel’s turn to be sampled.
If the user interrupt is set up to use ‘non-continuous’ mode, the start acquisition trigger is applied at
the start of every buffer received by the driver from the DLL. In ‘continuous’ mode, the start
acquisition trigger is applied only to the first buffer received by the driver from the DLL.
The following start acquisition start types are supported by PCI230+ and PCI260+ cards:
START_NOW Start acquisition as soon as possible (pre-trigger mode).
START_TRIG Start acquisition when trigger occurs.
When set to ‘START_NOW’, the trigger is not applied until the number of samples specified by the
hold-off value have been aqquired; data acquired before the trigger occurs is stored in the FIFO
(and read out of the FIFO) as normal. When set to ‘START_TRIG’, the hold-off value must be zero;
data acquired before the trigger occurs is discarded by the hardware.