Protocol Stack Trace Log

The protocol stack trace log provides the user with an indication of the Modbus messages received and sent by the Modbus RTU Slave Interface at the communications port level. Each logged message is time stamped.

The user may enable or disable trace logging by defining a trace log parameters record within the Modbus RTU Slave Interface configuration file.

When enabled, the Modbus RTU Slave Interface writes protocol stack trace messages to the file MRTUSI_RP.err in the log sub-directory of the Project root directory.


If the Project had been created in the directory C:\Program Files\GE Fanuc\Proficy CIMPLICITY\Projects\test\, then the trace message file specification is C:\Program Files\GE Fanuc\Proficy CIMPLICITY\Projects\test\log\MRTUSI_rp.err.

The following is an excerpt from an actual trace log file.

2000-10-09 09:56:19.511 <- 0103 00000018 45c0

2000-10-09 09:56:19.611 -> 0101 30000100020003000400050006000700080009000A000B000C000D000E000F001000110012001300140015001600170018 5EAF

2000-10-09 09:56:19.641 <- 0103 00180018 C5C7

2000-10-09 09:56:19.701 -> 0103 300019001A001B001C001D001E001F0020002100220023002400250026002700280029002A002B002C002E002F0030 8969

2000-10-09 09:56:19.741 <- 0103 00300018 45CF

2000-10-09 09:56:19.802 -> 0103 30003100320033003400350036003700380039003A003B003C003D003E003F004000410042004300440045004600470048 036D

2000-10-09 09:56:19.842 <- 0103 00480018 C5D6

2000-10-09 09:56:19.922 -> O1O3 300049004A004B004C004D004E004F0050005100520053005400550056005700580059005A005B005C005D005E005F0060 D84A

2000-10-09 09:56:20.012 <- 0103 00600004 4417

2000-10-09 09:56:20.102 -> 0103 080061006200630064 ED2C

2000-10-09 09:56:35.464 <- 8002 000000C8 678D

2000-10-09 09:56:35.554 -> 8002 195555555555555555555555555555555555555555555555555555 60E3

The format for a trace log message is:

<date> <time> <direction> <slave address><function code> <data> <CRC>


<date> is \the date the message was received or sent.

<time> is the time the message was received or sent.

<direction> is an arrow indicating whether the message is a request or response message.

Request (left arrow): <-

Response (right arrow): ->

Note: the remaining fields are displayed as hex values (two characters per byte).

<slave address> is the emulated slave device address.

<function code> is one byte representing the requested operation. If an exception response is generated, the high bit is set.

<data> is one or more bytes containing function parameters, data values, and/or exception code.

<CRC> is trailing two bytes containing the cyclical redundancy check value.

More information

Modbus RTU Slave troubleshooting.