User Manual DDS200 Digital Demodulation System 070-9952-00

Remote ControlTable 3–5: Definition of bits used in the STATus:QUEStionable RegisterBit No.DefinitionThis register is not usedÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁUse of the StatusReporting SystemFor an efficient use of the status reporting system, the information containedtherein has to be transferred to the controller and further processed. There arevarious methods which are described in the following. Detailed programexamples are given in Appendix D: Program Examples.ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁService Request, Use of Hierarchical Structure. Under certain conditions, theinstrument may send a service request (SRQ) to the controller. This servicerequest usually causes an interrupt at the controller to which the controllerprogram can respond by suitable actions. As shown in Figure 3–4 on page 3–22),a SRQ will always be triggered if one or several of the bits 2, 3, 4, 5 or 7 havebeen set in the Status Byte Register and enabled in the SRE. Each of these bitscombines the information from a further status register, from the error queue orthe output buffer. By setting the ENABle registers of the status registersaccordingly, any bit in any status register will be able to trigger a SRQ. To utilizethe possibilities of the service request, all bits in the enable registers SRE andESE should be set to “1”.Example (see also Figure 3–4 on page 3–22 and Appendix D: Program Examples):Use the *OPC command to generate a SRQ:1. Set bit 0 (Operation Complete) in the ESE.2. Set bit 5 (ESB) in the SRE.3. The instrument generates a SRQ upon completion of its settings.The SRQ is the only way for the instrument to become active on its own. Acontroller program should set the instrument so that a service request will begenerated in case of malfunctions. The program should suitably respond to theservice request. A detailed example of a service request routine is given inAppendix D: Program Examples.Serial Poll. Similar to the *STB command, the serial poll is used to query thestatus byte register of a device. Querying is implemented by interface messagesand is therefore much quicker. The serial poll method has already been defined inthe IEEE 488.1 standard and used to be the only standard method of querying thestatus byte register. This method also works with instruments which neitherconform to SCPI nor to IEEE 488.2.3–26 DDS200 Digital Demodulation System User Manual