Allen-Bradley 5069-SERIAL, User Manual, Page: 94 / 110

96 Rockwell Automation Publication 5069-UM003A-EN-P - May 2018
Appendix B Master Command List
Response
The addressed slave responds with its address and the function code followed
by the information field. The information field contains 1 byte describing the
quantity of data bytes to be returned. The contents of the registers requested
(DATA) are 2 bytes each, with the binary content right justified within each
pair of characters. The first byte includes the high-order bits and the second,
the low-order bits.
Because the slave interface is normally serviced at the end of the controller's
scan, the data reflect the register content at the end of the scan. Each PC limits
the quantity of register contents provided each scan; thus for large register
quantities, multiple PC scans are required, and the data that is provided is from
sequential scans.
In the following example, the register 30009 contains the decimal value 0.
Force Single Coil (Function Code 05)
Query
This Function Code forces one coil (Modbus 0x range) either ON or OFF.
Any coil that exists within the controller can be forced to either state (ON or
OFF). However, because the controller is actively scanning, unless the coil is
disabled, the controller can also alter the state of the coil. Coils are numbered
from zero (coil 0001 = zero, coil 0002 = one, and so on). The data value 65,280
(FF00 HEX) sets the coil ON and the value zero turns it OFF; all other values
are illegal and do not affect that coil.
Node Address Function Code Byte Count Data Input Register
High Data Input Register
Low Error Check Field (2
bytes)
0B 04 02 00 00 CRC