User Manual DDS200 Digital Demodulation System 070-9952-00

Remote ControlIEC/IEEE-Bus MessagesThe messages transmitted on the data lines of the IEC/IEEE bus (refer toAppendix A:IEC/IEEE-Bus Interface) can be subdivided into two groups:Interface messagesDevice-dependent messagesInterface MessagesInterface messages are transmitted on the data lines of the IEC/IEEE bus, withthe control line “ATN” active. They are used for communication between thecontroller and the instrument and can only be sent by a controller with controllerfunction on the IEC/IEEE bus.There are two groups of interface messages:Common commandsAddressed commandsCommon commands affect all devices connected to the IEC/IEEE bus withoutany addressing being required, whereas addressed commands only affect devicesaddressed as a listener. The relevant interface messages are listed in Appendix A:IEC/IEEE-Bus Interface.Device-DependentMessages (Commandsand Responses)The device-dependent messages are transmitted on the data lines of the IEC/IEEE bus with the control line “ATN” not active. The ASCII code is used fordata transmission. Device-dependent messages are differentiated according to thedirection in which they are sent via the IEC/IEEE bus.Commands. Commands are messages sent by the controller to the device. Theycontrol the device functions and request information. The commands aredifferentiated according to two criteria:1. According to the effect they have on the device:Setting commands trigger device settings (for example, resetting theinstrument or setting the receive frequency).Queries cause data to be provided for output via the IEC/IEEE bus (forexample, for device identification or query of the receive frequency).2. According to their definition in the IEEE 488.2 standard:Common commands are precisely defined in their function and notation inthe IEEE 488.2 standard. They refer to functions such as the management ofthe standardized status registers, resetting, and selftest.3–4 DDS200 Digital Demodulation System User Manual