ABB COMMANDER 300 Operating Instructions Manual

Also see for COMMANDER 300: Programming guide

Contents

28A3 Block Check CharactersThe block check character (BCC)transmitted is determined by the seven leastsignificant bits in the binary arithmetic sum ofa complete message (excluding parity bits).All characters transmitted before the BCCmust be included in the arithmetic sum. Referto Appendix A1 on page 25 for ASCIIcharacters.A3.1 BCC ExampleMessage – STXW02MV–50ETXFind the ASCII decimal equivalent of eachcharacter in the message, calculate thedecimal arithmetic sum and hence obtain thebinary arithmetic sum.STX = 2R = 820 = 482 = 50M = 77V = 86– = 455 = 530 = 48ETX = 3Only the seven least significant bits (LSB) ofthe binary arithmetic sum are required todetermine the BCC:MSB LSB11 1101110‘n’ is the BCC transmitted –see Appendix A1Arithmetic sum =494 decimal111101110 binaryA2 Non-volatile Memory LimitationsCaution. If the number of writecycles to any particular non-volatilememory register exceeds 104 cycles, thedata stored may not be retained.Any changes made to a parameter via theserial link, e.g. Control Set Point value, arestored in a non-volatile memory registerassigned to that parameter.The number of write cycles to a particularregister can be reduced by disabling non-volatile memory access when makingchanges to parameters which do not need tobe retained following a power-down. This isdone using the Non-volatile Save State (NV) –see Section 8.6.1, General Parameters.When the Non-volatile Save State is set to'Enable', any parameter changes made viathe serial link are written to non-volatilememory and are retained on power-down. Ifthe Non-volatile Save State is set to 'Disable',parameter changes made via the serial linkare not retained on power down.The Non-volatile Save State must be adjustedonly when necessary and must be reset tothe required state each time the instrument ispowered down, replaced with anotherinstrument or the host computer is powereddown.…APPENDICES

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