Disclaimer
Caterpillar disclaims any and all liability for use of third-party application software that will be used to control the Automatic Transfer Switches.
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Automatic Transfer Switches are often used in critical applications. Failure of an Automatic Transfer Switch to operate properly could cause property damage, personal injury or death. Extreme caution must be used when designing or using programming software that will communicate with the Automatic Transfer Switch. Improper use of the Modbus network variables will cause the Automatic Transfer Switch to malfunction. Always conduct a full test and debug of the programming software prior to installing and using it in the system. |
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ZNET200
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| Illustration 1 | g00835957 |
The ZNET200 network card enables the communication of the following information: the position of the transfer switch, the available source and the timers that are running. The information is sent to a remote annunciator panel, a PC, or a PLC via one pair of twisted wires. The wires should be 16 AWG. This cable is not included. The connections are located below the relay for the engine start timer.
Overview
The Modbus card is a network card that is designed for the MX200 controller. If the MX200 is ordered with the network card option, the network card will reside on the back of the controller. The network card will be part of the MX200 assembly. This card allows the controller to be available on a Modbus network as part of a master-slave circuit. The card allows a master to obtain information from the controller. An example of a master would be a programmable logic controller. Then, the master can perform the following operations: control, communication of data and monitoring.
Every Modbus network consists of one master and at least one slave device. All of the devices on the network are connected in parallel with twisted pair wiring. Each dependent device has a unique address. The address is a number from 1 to 247. This number allows the master to distinguish between the various dependent devices on the network. The address allows the master to send an inquiry to the device that is addressed. When the device that is addressed receives the command, the device will send an appropriate response back to the master. Refer to table 1 for a list of commands that are supported by the network card.
| Modbus Command | Description of the Modbus Command |
|---|---|
| 01 | Read the Status of the Coil. |
| 03 | Read the Holding Register. |
| 05 | Write to the Single Coil. |
| 06 | Write to the Single Holding Register. |
| 15 | Write to the Multiple Coils. |
| 16 | Write to the Multiple Holding Registers. |
The Modbus commands allow the master to read data from specific memory locations in the MX200. The commands also allow the master to write data to specific memory locations in the MX200. These memory locations make up the variables of the network for the MX200. These variables allow the reading of the following parameters from the MX200:
- status
- configuration
- voltage
- frequency
- serial number
- time on emergency
- number of transfers
- values of the timers
- pickup values
- dropout values
LED Indicator
The Modbus card has 10 LED indicators. These LED indicators display the address of the card. The first LED from the bottom indicates that the card is receiving information. The second LED indicates that the card is transmitting information. When data has been successfully transmitted the second LED will illuminate for 0.1 seconds. When data has been successfully received, the first LED will illuminate for 0.1 seconds. If additional data is transferred before 0.1 seconds, the respective LED will remain illuminated for another 0.1 seconds. LED indicators 3 through 10 display the address of the MX200 as a binary number. Each LED corresponds to a bit. Table 2 shows the 10 LED indicators.
| LED 10 - 27 |
| LED 9 - 26 |
| LED 8 - 25 |
| LED 7 - 24 |
| LED 6 - 23 |
| LED 5 - 22 |
| LED 4 - 21 |
| LED 3 - 20 |
| LED 2 - Transmit |
| LED 1 - Receive |