Sample: Multiple register access
This sample explains the access to the register of aTwinCAT system via Modbus.
The Modbusaddress 0x3000 is mapped by the default-configuration to the memory area of the plc (ADS-Indexgroup 0x4020)
PROGRAM MAIN
VAR
ipAddr : STRING(15) := '';
M0 AT%MB0 : ARRAY [0..3] OF WORD;
nValue : ARRAY [0..3] OF WORD :=0,10,100,1000;
fbWriteRegs : FB_MBWriteRegs;
bWriteRegs : BOOL;
END_VAR
IF NOT bWriteRegs THEN
nValue[0]:= nValue[0]+1;
nValue[1]:= nValue[1]+1;
nValue[2]:= nValue[2]+1;
nValue[3]:= nValue[3]+1;
bWriteRegs :=TRUE;
fbWriteRegs.sIPAddr :=ipAddr;
fbWriteRegs.nQuantity := 4;
fbWriteRegs.nMBAddr := 16#3000;
fbWriteRegs.cbLength := SIZEOF(nValue);
fbWriteRegs.pSrcAddr := ADR(nValue);
fbWriteRegs.tTimeout := T#5s;
fbWriteRegs(bExecute:=TRUE);
ELSE
IF NOT fbWriteRegs.bBUSY THEN
bWriteRegs :=FALSE;
END_IF
fbWriteRegs(bExecute:=FALSE);
END_IF
The array arrValue will be written to the memory area of the plc (M0) by a rising edge on bWriteRegs.
See also