APPENDIX 4
SENDING COMMANDS TO THE DFC
RS485
The standard DFC comes with an RS485 interface. The protocol described below
allows for the unit using either a custom software program or a “dumb terminal”.
All values are sent as printable ASCII characters. The start character is always !and
the command string is terminated with a carriage return (line feeds are
automatically stripped out by the DFC:
!<Addr>, <Cmd>,Arg1,Arg2,Arg3,Arg4<CR>
WHERE:
! Start character
Addr RS485 device address in the ASCII representation of
hexadecimal (00 through FF are valid).**
Cmd The one or two character command from the table above.
Arg1 to Arg4 The command arguments from the table above.
Multiple arguments are comma delimited.
CR Carriage return character.
** Default address for all units is 11.
Several examples of commands follow.
All assume that the DFC has been configured for address 15 (0F hex) on the RS485 bus:
1. To put the unit in digital mode: !0F,M,D<CR>
The DFC will reply: !0FMD<CR>
2. To set the flow of 50% of FS: !0F,S,50.0<CR>
The DFC will reply: !0FS50.0<CR>
3. To get a flow reading: !0F,F<CR>
The DFC will reply: !0F50.0<CR>
(Assuming the flow is at 50% FS)
4. Set the high alarm limit to 5% above Set point: !0F,A,H,5.0<CR>
The DFC will reply: !0FA5.0<CR>
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