User Manual DDS200 Digital Demodulation System 070-9952-00

Remote ControlSyntax errors in the command are recognized and passed on to the statusreporting system. The remaining part of a command line after a syntax error willbe further analyzed as far as possible and processed.If a terminator or a DCL is identified, the command identification requests thedata set to execute the setting commands in the device hardware. The commandidentification is then immediately ready to process a new command. This meansthat addtional commands can be processed while settings are being made in thehardware (overlapping execution).Data Set and DeviceHardwareThe term “device hardware” refers to the part of the instrument that performs theinstrument function proper, such as signal generation and measurements. Thisdoes not include the controller.The data set exactly represents the hardware functions in the software. IEC/IEEE-bus setting commands cause a modification in the data set. The data setmanagement enters the new values (for example, frequency) into the data set, butpasses them on to the hardware only when requested by the command identificationto do so. Since this request is always made at the end of a command line, thesequence of the setting commands in the command line is irrelevant.Immediately before the data are passed on to the device hardware, they areverified for compatibility both with the other data and with the device hardware.If execution of the setting commands is not possible, an execution error messagewill be sent to the status reporting system. All modifications to the data set willbe ignored and no new setting made in the device hardware. Due to the delayedverification and hardware setting, illegal device states may temporarily be setwithin a command line without causing an error message. At the end of thecommand line, a legal device status must be restored.Prior to the data transfer to the hardware, the settling bit is set in theSTATus:OPERation Register (refer to STATus:OPERation Register on page 3–25).The hardware carries out the setting and the bit is reset as soon as settled state isreached. This mechanism can be used for synchronization of the commandprocessing.IEC/IEEE-bus queries cause the data set management to send the desired data tothe output unit.Status Reporting SystemThe status reporting system collects information about the device status andmakes it available to the output unit on request. Structure and function aredescribed in detail in Status Reporting System on page 3–19.DDS200 Digital Demodulation System User Manual 3–17