HP VXI Using a Service Request to Detect Errors

Chapter 2

18 Programming the Status System

-- Read the Status Byte using ireadstb. ireadstb returns the RQS (request for service) bit in bit 6 of the status byte. After issuing a ireadstb, RQS is cleared indicating that the Service Request is being acknowledged. A new SRQ will not be issued unless RQS is cleared. Using *STB? will return the Master State Summary in bit 6 and does not affect RQS.

-- Check if the MAV bit (bit 4) is set to indicate that a message is available. If the MAV bit is set, then a message is available and the SRQ handler can process the message. In this example, the output queue is read using iscanf.

-- Check if the Standard Event Status summary bit (bit 5) is set. If the bit is set then read the Standard Event Status Group’s Event Register to determine which event(s) caused the SRQ. Check for Command Error (bit 5), Execution Error (bit 4), Device Dependent Error (bit 3), or Query Error (bit 2). If found, read the error queue with SYST:ERR? to print out error messages.

• Enable SRQ Handler in SICL with ionsrq.

• Enable MAV bit (Message Available Bit) and Standard Event Status Register Summary Bit in the Status Byte Enable Register (e.g. *SRE 48). This will cause an SRQ to arrive when there is a message in the output queue or when the summary bit is set in the standard event status register.

• Enable the Command Error, Execution Error, Device Dependent Error, and Query Error enable bits in the Standard Event status enable register (e.g. *ESE 60). This will cause the summary bit of the standard event status register to be set when an error occurs.

Define a SRQ Handler which does the following:

•

The following example program sets up an SRQ handler to be called when SCPI errors are detected using the Standard Event Status Register. The program then prompts for SCPI commands. If the SCPI command results in data in the output queue (such an query command) or an error, then the SRQ handler is called and the data is printed.

The following summarizes the procedure used:

Using a Service Request to Detect Errors

iclose(id);

}