ProSoft Technology MVI71-MNET - Manual (Page 91)

Reference MVI71-MNET ♦ PLC Platform
User Manual Modbus TCP/IP Interface Module
ProSoft Technology, Inc.
Page 91 of 109
June 23, 2009
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 will reflect the register content at the end of the scan. Each PC will
limit the quantity of register contents provided each scan; thus for large register
quantities, multiple PC scans will be required, and the data provided will be form
sequential scans.
In the example below the register 3009 contains the decimal value 0.
Adr Func Byte Count Data Input Reg Hi Data Input Reg Lo Error Check Field
11 04 02 00 00 E9
5.7.5 Force Single Coil (Function Code 05)
Query
This message forces a single coil 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) will set the coil ON
and the value zero will turn it OFF; all other values are illegal and will not affect
that coil.
The use of Slave address 00 (Broadcast Mode) will force all attached Slaves to
modify the desired coil.
Note: Functions 5, 6, 15, and 16 are the only messages that will be recognized as valid for
broadcast.
The example below is a request to Slave number 11 to turn ON coil 0173.
Adr Func Data Coil # Hi Data Coil # Lo Data On/off Ind Data Error Check Field
11 05 00 AC FF 00 CRC
Response
The normal response to the Command Request is to re-transmit the message as
received after the coil state has been altered.
Adr Func Data Coil # Hi Data Coil # Lo Data On/ Off Data Error Check Field
11 05 00 AC FF 00 CRC
The forcing of a coil via MODBUS function 5 will be accomplished regardless of
whether the addressed coil is disabled or not (In ProSoft products, the coil is only
affected if the necessary ladder logic is implemented).