User`s manual

APPENDIX A - DATA LOGGER A-3
CDS7324 (FORMERLY LSF-0819)
Rev. A INSTALLATION & USER’S MANUAL
A.1.3.3 Trigger input
The trigger input is selected by setting the trigger channel parameter trigger_field_number (field number 1756) to
the field number of the parameter that is used for triggering the sampling process. The coupling is selected by
setting the trigger_coupling (field number 1757) parameter:
0x00 - ac coupled trigger input
0x01 - dc coupled trigger input
0x02 - bitmask trigger
The trigger level can be set with the trigger_level_xxxxx parameters. The data type has to match the data type of
the parameter sampled. For example, if a 16-bit integer value is used for triggering, then trigger_level_16-bit has
to be set. The trigger levels also hold the bit mask for the bit mask trigger mode. Only bits that are 1 in the mask
are used for triggering. More than one bit can be set to one.
The trigger slope parameter trigger_slope (field number 1758) selects if triggering is done on the rising or falling
edge of the trigger input. If bit mask trigger is used a 0-1 transition is taken as a rising and a 1-0 transition is taken
as a falling input signal.
0x01 - trigger on rising edge
0x02 - trigger on falling edge
0x03 - trigger on both edges
Normally the sampling would start at the trigger event. If the sampling has to be delayed, or if the samples shall
be taken before the trigger event, the position of the trigger event within the samples can be selected using the
trigger delay parameter trigger_delay (field number 1765). It holds the number of the samples before the trigger
event.
A.1.4 Data Access
A.1.4.1 Scaled data access
To improve performance and to make the interface easier, there are parameters available that allow the reading
of scaled data for each channel with only one byte per channel and sample transmitted.
The offset data_logger_scaling_offset (field number 1769) is added to the value and the result is then multiplied
with the scaling factor data_logger_scaling_factor (field number 1768). The result is then rounded to the nearest
signed 8-bit value and can be accessed by reading the parameter data_logger_channel_x. The number of bytes
transmitted is always DLGDIS (500). The transmitted data can be selected from the sampled data by writing to
the parameter data_logger_sample_number (field number 1770) before reading the data which represents the
number of the first data sample to be transmitted relative to the trigger position.