Proper EOL Termination - Metasys - LIT-12012443 - Software Application - MS-FIT100-0 Field Inspection Tool

MS-FIT100-0 Field Inspection Tool User Guide

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MS-FIT100-0 Field Inspection Tool
Document type
User Guide
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It is recommended that most FCBs should have an EOL termination set on each controller at the end of each bus segment. Proper EOL termination is needed for reliable communications. The FIT tool has an EOL termination circuit that can be turned On or Off by the user. See Table 7 for the EOL switch positioning.

Table 1. EOL Termination Switch Positions
Mode Switch Position
1-ON-1 Mode EOL circuit is On.
Monitor Mode EOL circuit is Off.
Scan Bus Mode EOL circuit is Off.

The user can override the EOL operation by using the EOL Command under the System menu. If the supervisory controller is not connected to the bus, use the FIT to start communications in Scan Bus mode.

Note: If the FIT is connected at the end of the bus where the supervisory controller would be and the supervisory controller was an EOL, then it would be advisable to set the EOL switch to On in the FIT System menu.

The bus is now properly terminated as if the supervisory controller was in place. The EOL On command allows the FIT to act as an active termination that can be placed anywhere on the bus to help troubleshoot bus communication issues.

Keep in mind the FCB EOL termination attribute is limited to Johnson Controls manufactured products that have a built-in EOL switch. The location of other EOL devices and jumpers is not detected. Not all legacy Johnson Controls; controllers support the EOL termination attribute. Figure 18, Figure 19, and Figure 20 show different scenarios, how the FIT should be configured, and what EOL switches are monitored.

On an SAB, the minimum requirement is that the EOL termination must be enabled on at least one device on the bus, and because a SAB supervisor (a controller like the FEC or VMA) always has EOL termination enabled, this requirement is always met; however, for enhanced bus performance, it is preferable to have EOL termination enabled on the devices at each end of the SA Bus.