Fluke PM6685 Status Condition Registers, Why Two Types of Registers?, Set up, Check & Action, Sre

Using the Subsystems

–*ESR? Reads the Standard Event Status register

–:STATus:OPERation? Reads the Operation Status Event register

–:STATus:QUEStionable? Reads the Questionable Status Event register

–:STATus:DREGister0? Reads Device Event register

When you read these registers, you will clear the register you read and the sum- mary message bit in the status byte.

You can also clear all event registers with the *CLS (Clear Status) command.

￿Status Condition Registers

Two of the status register structures also have condition registers: The Status Op- eration and the Status Questionable regis- ter.

The condition registers differ from the event registers in that they are not latched. That is, if a condition in the counter goes on and then off, the condi- tion register indicates true while the con- dition is on and false when the condition goes off. The Event register that monitors the same condition continues to indicate true until you read the register.

–:STATus:OPERation:CONDition?

Reads the Operation Status Condition reg- ister

–:STATus:QUEStionable:CONDi- tion? Reads the Questionable Status Condition register

Reading the condition register will not af- fect the contents of the register.

Why Two Types of Registers?

Let’s say that the counter measures con- tinuously and you want to monitor the

measurement cycle by reading the Opera- tion Status register.

Reading the Event Register will always show that a measurement has started, that waiting for triggering and bus arming has occurred and that the measurement is stopped. This information is not very use- ful.

Reading the Condition Register on the other hand gives only the status of the measurement cycle, for instance “Mea- surement stopped”.

￿Although it is possible to read the condition registers directly, we recommend that you use SRQ when monitoring the measure- ment cycle. The measurement cycle is disturbed when you read condition registers.

￿Summary:

The way to work when writing your bus program is as follows:

Set up

–Set up the enable registers so that the events you are interested in are summa- rized in the status byte.

–Set up the enable masks so that the condi- tions you want to be alerted about generate SRQ. It is good practice to generate SRQ on the EAV bit. So, enable the EAV-bit via

*SRE.

Check & Action

–Check if an SRQ has been received.

–Make a serial poll of the instruments on the bus until you find the instru- ment that issued the SRQ (the instru- ment that has RQS bit true in the Sta- tus Byte).

Status Subsystem 6-19