User manual

IEC61131 User and Reference Manual
April 22, 2008
409
Enron Modbus Function Codes
The following table shows the implemented function codes for Enron Modbus. The maximum
number of registers that can be read or written with one message is shown in the maximum
column. The slave device may support fewer registers than shown; consult the manual for
the device for details.
Functions 129, 130, 132, 133, 135, 136, 138, and 139 may be broadcast, but some Enron
Modbus slave devices may not support broadcast messages. Consult the manual for the
device for details.
Function
Name
Description
Maximum
128
Read Enron Boolean
Read Enron Boolean registers
2000
129
Write Enron Boolean
Write Enron Boolean register
1
130
Write Enron Multiple
Boolean
Write Enron Boolean registers
880
131
Read Enron Short Integer
Read Enron short integer
register
125
132
Write Enron Short Integer
Write Enron short integer
register
1
133
Write Enron Multiple Short
Integer
Write Enron short integer
registers
60
134
Read Enron Long Integer
Read Enron long integer register
62
135
Write Enron Long Integer
Write Enron long integer register
1
136
Write Enron Multiple Long
Integer
Write Enron long integer
registers
30
137
Read Enron Floating Point
Read Enron floating-point
register
62
138
Write Enron Floating Point
Write Enron floating-point
register
1
139
Write Enron Multiple Floating
Point
Write Enron floating-point
registers
30
Sending Messages
A master message is initiated in one of five ways:
 using the master_message function from a C or C++ application program; or
 using the MSTR function block from a TelePACE ladder logic program; or
 using the MSIP function block from a TelePACE ladder logic program; or
 using the master function in an ISaGRAF program; or
 using the masterip function in an ISaGRAF program.
These functions specify the port on which to issue the command, the function code, the type
of station addressing, the slave station number, and the location and size of the data in the
slave and master devices. The protocol driver, independent of the application program
receives the response to the command.
The application program detects the completion of the transaction by:
 calling the get_protocol_status function in a C application program; or
 using the output of the MSTR function block in a TelePACE ladder logic program; or
 using the output of the master function in an ISaGRAF program.