Agilent 33120A User's Guide

Chapter 4 Remote Interface ReferenceRS-232 Interface ConfigurationDTR / DSR Handshake ProtocolThe function generator is configured as a DTE (Data Terminal Equipment)device and uses the DTR (Data Terminal Ready) and DSR (Data Set Ready)lines of the RS-232 interface to handshake. The function generator usesthe DTR line to send a hold-off signal. The DTR line must be TRUEbefore the function generator will accept data from the interface. Whenthe function generator sets the DTR line FALSE, the data must ceasewithin 10 characters.To disable the DTR/DSR handshake, do not connect the DTR line and tiethe DSR line to logic TRUE. If you disable the DTR/DSR handshake, alsoselect a slower baud rate (300, 600, or 1200 baud) to ensure that thedata is transmitted correctly.The function generator sets the DTR line FALSE in the following cases:1 When the function generator’s input buffer is full (when approximately100 characters have been received), it sets the DTR line FALSE (pin 4 onthe RS-232 connector). When enough characters have been removed tomake space in the input buffer, the function generator sets the DTR lineTRUE, unless the second case (see below) prevents this.2 When the function generator wants to “talk” over the interface (whichmeans that it has processed a query) and has received a message terminator, it will set the DTR line FALSE. This implies thatonce a query has been sent to the function generator, the controllershould read the response before attempting to send more data. It alsomeans that a must terminate the command string. After theresponse has been output, the function generator sets the DTR lineTRUE again, unless the first case (see above) prevents this.The function generator monitors the DSR line to determine when thecontroller is ready to accept data over the interface. The functiongenerator monitors the DSR line (pin 6 on the RS-232 connector) beforeeach character is sent. The output is suspended if the DSR line isFALSE. When the DSR line goes TRUE, transmission will resume.198