Page 5-12
MiniCapt Remote Microbial Air Sampler Operations Manual
Chapter 5 Modbus Protocol
Data Register Processing
Data Register Processing
The unit can provide real-time data or queued data or both. There is only one section
of input registers assigned for data to handle this information.
If the unit is setup to queue data then the data shown is the oldest data in the queue.
The data available coil (00/02) will be set on a read if there is data in the queue. The
data available coil (00/02) can be cleared and written (i.e., set coil to zero) in which
case that data element shown is popped-off of the queue. If there is more data in the
queue, the new data will be shown and the data available coil (00/02) will be set again
right away. If there is no more data in the queue, the data available coil (00/02) will only
be set again once the next sample is completed.
If the queue is set to one, then the data shown is always the last data processed
and is representative of real-time data only. Since the queue is circular - the next
sample will replace the single one in the queue.
If the queue is set to a value greater than one, then the data shown is the oldest
in the queue. Any data collected once the queue is full will cause the oldest data
to be discarded.
Queued data will always be available - even when not sampling.
If there is no data available - the input registers (associated with the actual sample
collected) will yield zeros. This is done instead of generating an execution exception so
that the customer can simply read the data packet, along with the Device Status (i.e.,
current coil settings), in one command.
