ABB COMMANDER 300 Operating Instructions Manual

Also see for COMMANDER 300: Programming guide

Contents

68 COMMUNICATION8.1 CommunicationBetween Master and SlavesThe commands from the master are codedas single characters as follows:R – ‘Read’ (read parameters)M – ‘Multiple Read’ (read a selectionof parameters)W – ‘Write’ (write new parametervalues).8.1.1 MnemonicsEach mnemonic for the C300 Controllerparameters comprises two characters – seeSection 8.6.8.1.2 Relay LogicEquation (Q1, Q2)The alarm relay assignment is transmitted inthe format in which it is displayed.✶ Note. The terminator is transmittedas a ‘#’, but appears on the display as ‘W’.8.2 Command Format– Figs. 8.1 to 8.3The protocol is based on ANSI-X3.28-1976-2.5-A4. Entries are made directly from thehost computer using the command formatshown in Figs. 8.1 to 8.3.8.2.1 Term Clarificationfor Command FormatStart – one ASCII control character (always‘STX’) signifying the start of transmission.Command – one character, R, M or W – seeSection 8.1.Instrument Identification – two charactersidentifying the C300 Controller, 01 to 99.Parameter – two-character mnemonicselected from Section 8.6.Sign – one character:‘+’ – parameter value is positive(optional)‘–’ – parameter value is negative.Data – usually up to six characters (includingdecimal point) used to write a new parametervalue. However, up to 12 characters may beused if Alarm Relay Assignment is beingcarried out, i.e. using mnemonics Q1 andQ2.Limiter – one character (always ‘ETX’)signifying the end of data transmission.Block Check Character (BCC) – one character,the arithmetic sum of the complete message(excluding parity bits), transmitted by thehost computer for error detection – seeAppendix A3 on page 28.