Chapter 6. Serial I/O, SNP & RTU ProtocolsGFK-2222AD April 2018 245Message (15): Force Multiple OutputsFormat:Address Numberof PointsError CheckFunc15QueryNormal ResponseAddress Error CheckFunc15ByteCount DataStartingPointPoint No.Numberof PointsStartingPointPoint No.Figure 60: RTU Force Multiple Outputs Message FormatQuery:▪ An Address of 0 indicates a broadcast request. All slave stations process a broadcast request and noresponse is sent.▪ The value of the Function code is 15.▪ The Starting Point Number is two bytes in length and may be any value less than the highest outputpoint number available in the attached CPU. The Starting Point Number is equal to one less than thenumber of the first output point forced by this request.▪ The Number of Points value is two bytes in length. The sum of the Starting Point Number and theNumber of Points value must be less than or equal to the highest output point number available inthe attached CPU. The high order byte of the Starting Point Number and Number of Bytes fields issent as the first byte in each of these fields. The low order byte is the second byte in each of thesefields.▪ The Byte Count is a binary number from 1 to 256 (0 = 256). It is the number of bytes in the Data fieldof the force multiple outputs request.▪ The Data field is packed data containing the values that the outputs specified by the Starting PointNumber and the Number of Points fields are to be forced to. Each byte in the Data field contains thevalues that eight output points are to be forced to. The least significant bit (LSB) of the first bytecontains the value that the output point whose number is equal to the starting point number plusone is to be forced to. The values for the output points are ordered by number starting with the LSBof the first byte of the Data field and ending with the most significant bit (MSB) of the last byte of theData field. If the number of points is not a multiple of 8, then the last data byte contains zeroes inone to seven of its highest order bits.Response:▪ The descriptions of the fields in the response are covered in the query description.Note: The force multiple outputs request is not an output override command. The outputsspecified in this request are ensured to be forced to the values specified only at the beginningof one sweep of the user logic.
