This discussion assumes you want the Babel Buster SP (SPX) to be the Modbus TCP Master. Let's review the setup procedure for a single Modbus read map. We suggest starting with one register. Once you get that working, proceed to fill up the table.

First, go to the IP Network Devices page and make sure you have the IP address and port number set. Unless instructed otherwise, use port 502.

Next, go to the Click Read Map page (below) and click the "1" in the left column. This takes you to the expanded view of map #1.

To get started, you must enable some maps. Enter a number greater than zero in the # Client Read Maps Enabled window at the bottom of the expanded view page (below) and click Update.

Next, select a register type, a register number, a device (from list created above), and a local register number to store the data in. If any of the red check marks shown below are "none" or zero, you will get no action even attempted. Make sure the IP address matches whatever you have your Modbus device set to. If you are uncertain what IP address it is set to, you need to consult the manufacturer's documentation for that equipment before proceeding.

The following example shows the only non-zero entries required to successfully read holding register #1 from "My Modbus Device" and store the data in local register #1. Once these (or comparable) entries have been made, click the Update button.

At this point, you can go to the data page (below) and see if you have data showing up. If you get no data, there is a problem.

If you are getting no data, check the Error Codes page (below). Here we see that the "No Responses" is some number greater than total messages. Zero total messages means we never succeeded in making a TCP connection.

Check the error codes registers for further definition of what the problem is. In the example below, we see that the error code for our device, TCP device #1 (from list above), is 9516. Decoding this from the information in the Quick Help section of that page in the device, we see that we have a socket error, and the socket error code is 516, which means "timeout" (resulting from no TCP connection).

Error code registers are automatically named -Sys Error, Fn #n for system errors, -TCP error, device #n for TCP device errors, and -RTU error, device #n for Modbus RTU errors or BACnet device errors. In each instance of "device", the "n" is device number as referenced on other pages.

Error encoding for devices: ABCCC where A=exception codes 1..3 (4), B=error code as follows, and CCC=rule number:

Error code B indicates the following errors:
1 = Transaction ID out of sync
2 = Exception code returned by remote device
3 = Function code mismatch (bad packet)
4 = Inusfficient data (bad packet)
5 = No response from remote device, timed out
6 = CRC error in received packet
9 = Socket error (CCC=error code, see below)

Error code A indicates the following exception codes only when B is code 2 indicating an exception code was returned:
1 = Illegal function code
2 = Illegal data address (the requested register does not exist in the device)
3 = Illegal data value
4 = other/out of range code

Some example error codes that are common: 5001 (05001) means no response from device at map rule #1.  Example 2: 22005 means exception code 2 occurred on map rule #5. This generally means the register you attempted to access is not available at that remote device. Example 3: 6039 means a CRC error was received at map rule #39, and generally indicates a transmission error due to noise on the line.

Special case of socket error: Code will be >9000, and 9xxx will indicate socket error code xxx. Common socket codes include the following:
104 - Connection reset by peer
105 - No buffer space available
111 - Connection refused
112 - Address already in use
113 - Connection aborted
114 - Network unreachable
116 - Connection timed out
117 - Host is down
118 - Host is unreachable401 - General socket error
516 - Timeout, no response from remote device