Omega Vehicle Security 1400 Reading the Acquisition Buffer, PRINT#1,OUTPUT07 U6X, Input, Print

Configuration Aspects for Programmers Appendix B

Reading the Acquisition Buffer

The three previous sections briefly discussed how the acquisition buffer may be accessed and read. In this section the methods by which the acquisition buffer is read will be discussed in more detail.

As mentioned earlier, the Acquisition Buffer is organized as a FIFO (First In, First Out). As such all data read from the Acquisition Buffer will be the oldest available data. Furthermore, once the data has been read from the buffer it is no longer available. Upon completion of a read operation, the data associated with the read operation will be deleted.

The Read Acquisition Buffer (R) command is the command by which Acquisition Buffer data is read. You can use this command to read anywhere from one scan to all the scan data currently residing in the buffer. This command has the following valid forms:

R1 Read the oldest scan available.

R2 Read the oldest trigger block available.

R3 Read all available scan data.

When an R command is issued, ChartScan checks to see if the request can be fulfilled. If s, the requested scan data is moved from the Acquisition Buffer to the Output Queue where it waits until the controller initiates transfer.

Note: The request may will not be fulfilled if either (1) no channels are configured, or (2) the amount of scan data requested is not available. If either of these is true a Conflict Error will be posted. The R1 and R3 commands require that at least one scan be available and the R2 command requires that at least one complete trigger block be available.

The Scan Available bit in the Status Byte (STB) Register can be used to determine whether or not the Acquisition Buffer is empty. This bit is set when at least one scan is available in the buffer. The Buffer Status String (U6) command may also be used to retrieve more detailed information about the state of the Acquisition Buffer.

The following are simple examples to illustrate the uses and effects of all three R command types.

Note: Although not mentioned prior to these examples, the responses to all queries (U6, R1, R2, etc.) can be configured with specific field separators and response terminators. For detailed instructions on setting query terminators, refer to the Q command description in Appendix D.

The R1 command will read the oldest scan in the oldest trigger block. For instance:

PRINT#1,"OUTPUT07; U6X"		‘ Request the current status of the Acquisition Buffer
PRINT#1,"ENTER07"		‘	Retrieve it.
INPUT	A$	‘	Screen shows...
PRINT	A$

0000006,0020216,-00000100,12:51:43.100,03/24/97,00000100,01:53:01.300,03/24/97,00000250,01

The above response indicates that there are 6 trigger blocks currently defined in the Acquisition Buffer and there are 20216 total scans in the buffer. Furthermore, it shows that the current read pointer is at scan # -100 in the 1st trigger block. To retrieve that scan perform the following:

PRINT#1,"OUTPUT07;R1X"	‘ Request the oldest scan
PRINT#1,"ENTER07"	‘ Retrieve it.
INPUT A$	‘ Screen shows (4 channels are configured)...
PRINT A$
+0234.20-0019.40+0001.40+0023.60
PRINT#1,"OUTPUT07; U6X"	‘ Request the current status of the Acquisition Buffer
PRINT#1,"ENTER07"	‘ Retrieve it.
INPUT A$	‘ Screen shows...
PRINT A$

0000006,0020215,-00000099,12:51:43.100,03/24/97,00000100,01:53:01.300,03/24/97,00000250,01

Notice that after reading the scan there are now 20,215 scans in the buffer and the current read pointer is now at scan # -99.

B-24 ChartScan User’s Manual