Delta RMC151 - Manual (Page 189)

3 Controller Features
Use the Plot State register to tell whether the plot is continuously capturing. The plot
is continuously capturing when the Plot State register is 0:
0 = not triggered, 1 = capturing, 2 = complete.
2. Write 2 to the Upload Mode/Status Register
Write a value of two (2) to the Upload Mode/Status Register. This sets the upload
mode to "continuous" and resets the Current Index register to zero. The Current
Index register indicates which sample number of the plot the next read will start at.
When it resets to 0, the next read will start at sample 0. In continuous mode, the
Current Index may become very large. It is a 32-bit number and will wrap when it
reaches its limit.
3. Write the Requested Read Samples per Data Set
Write the number of samples per data set that you would like returned per read to the
Requested Read Samples register. The minimum length of the read itself will be
affected by this value, as described later.
4. Read the Plot Data Starting from Dynamic Plot Upload register #0
Upload Mode 2 will return valid data only if there is enough captured data to fill the
request. If there is not enough captured data, the Samples Uploaded register will
return 0. Therefore, the typical method of reading a plot is to keep reading the plot data
and only using the data when the Samples Uploaded register is non-zero.
If the read falls too far behind to keep up with the data, the Upload Status bits will be
set to two (2) to indicate an overrun error. To recover, restart the plot by writing zero
(0) to the Current Index register.
Each time you read the plot data, start the read at Dynamic Plot Upload register #0.
The Current Index register will automatically be set to the index of the first sample of
the data returned in the read. Each read will return Dynamic Plot Upload registers 0-
4 and the plot samples beginning at the sample number in the Current Index register.
Since each read includes registers 0-4, you will have access to this information after
each read.
To read the plot data repeat these steps:
a. Calculate the Length of the Read.
The length of the read must be long enough to receive the number of samples per
data set you wrote to the Requested Read Samples register. In addition to
returning Dynamic Plot Upload registers 0-4, each read will return an equal
number of samples from each data set in the plot. Use the following equation to
calculate the length of the read based on how many samples you wish to read:
length = (Requested Read Samples) x (# of data sets) + 5
The number of samples should not be more the number of samples in the plot.
Typically, you will make this calculation once and then always make reads of the
same length.
b. Read from Dynamic Plot Upload register #0
Read from the Dynamic Plot Upload register #0 with the length calculated in step
a.
c. Do any Error Checking
If you wish, you can use Dynamic Plot Upload registers 0-4 to do error checking,
as described below:
• Verify that the Upload Status is 0, meaning no errors have occurred.
If the Upload Status is 1, the plot has been triggered, completed capturing,
and has been completely uploaded. To recover, issue the Rearm Plot (103)
command to set it to continuous capture.
If the Upload Status is 2, the capturing data overran the data you were
going to read. To recover from this error, write zero (0) to the Current Index
register, which will restart the plot. You will have to restart reading the plot
data.
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