Problem Solution Overview

We performed testing between the subject device and ProSoft Technology's 3100-MCM & 3150-MCM product.

Solution Brief

Our testing generated the following results:

• We were able to successfully communicate with the device. (see below for configuration parameters used during the testing)
• The product supports Modbus function codes 1, 2, 3, 4, 5, 6, 15, 16 for data movement.

The purpose of our testing is to assure a level of compatibility in the communications between the two products. Through this testing, we attempt to identify problem areas that may arise when implementing the interface in the field.

Configuration:

The product testing was performed with the following settings.
Baud: 9600
Parity: None
Stop: 1
Mode: RTU Master Mode
Physical Connection: RS-485 (2 wire connection)

The Module Configuration used in our testing was as follows:

This configuration, in combination with the example ladder logic referenced below, generates the following memory map:

N10:0 to N10:129 - Slave Data
N10:200 to N10:249 - Write Data

N10:130 to N10:149 - Slave Error Table (Contains revision level information also)
N10:150 to N10:199 - Master Error Table (Contains status of commands for diagnostics)

Command List:

The following command list shows some of the commands which were used to test the communications:

Our test command list performs the following functions.

1. N7:50 This command reads analog output current. Value is stored at N10:0.
2. N7:60 This command reads alarm, fault, and analog output status. Value is stored at N10:1
3. N7:70 This command reads the Active Flag for Meter run 1.
4. N7:80 This command reads number of successful calibrations. Value is stored at N10:2.
5. N7:90 This command clears latched alarms and faults conditionally. Value read from N10:200.

Cable Connection:

The physical connection which was used during testing was as follows:

For ease of installation, termination on the ProSoft module was accomplished using our screw termination adaptor for the DB-9 plug. A similar screw termination plug is also available for the DB-25 required for the 3100-MCM. The part number for these is:

1451-9F: DB-9 to RS-422/RS-485 Screw Terminals (for 3150-MCM)
1452-25M: DB-25 to RS-422/RS-485 Screw Terminals (for 3100-MCM)