GE Monogram GFK-1115 manual Bus Length, Baud Rate Selection

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Bus Length

The maximum bus length for shielded, twisted-pair cable is 7500 feet. Some cable types are restricted to shorter bus lengths. For example, for buses with a total cable length of 100 feet to 2000 feet Belden 9182 or Alpha 9823 or Belden 89182 can be used. In turn, the bus length determines which baud rate can be selected. If the application requires greater bus length, fiber optics cable and modems can be used, as explained later in this chapter.

If the application requires greater bus length, fiber optics cable and modems can be used; refer to the Genius I/O System and Communications User’s Manual (GEK-90486-1).

Baud Rate Selection

A Genius I/O or communications bus can operate at one of four baud rates: 153.6 Kbaud standard,

153.6Kbaud extended, 76.8 Kbaud, or 38.4 Kbaud. Follow these guidelines when selecting the baud rate for a bus:

1. All devices on a bus must operate at the same baud rate (other busses in the system can operate at different baud rates).

2. If there are any older Genius products on the bus (catalog numbers IC660CBDnnn, IC660CBSnnn, IC660CBAnnn, IC660HHM500, or IC660CBB900/901), the bus must be set up to use 153.6 Kbaud standard.

3. If the cable length is between 4500 and 7500 feet, you must select 38.4 Kbaud. This data rate only supports a maximum of 16 device on the bus.

4. If the cable length is between 3500 and 4500 feet, select 76.8 Kbaud.

5. If cable length is between 2000 and 3500 feet, select 153.6 Kbaud extended.

6. If the cable length is less than 2000 feet, either 153.6 Kbaud standard or 153.6 Kbaud extended can be used. The products are set to operate at 153.6 Kbaud standard when shipped from the factory. The use of 153.6 Kbaud extended is recommended, especially if the system will include a dual bus with Bus Switching Modules.

In noisy environments, 153.6 Kbaud extended provides improved noise immunity with little effect on bus scan time. If a system is experiencing excessive blinking of the bus controller's COMM OK light, or if the I/O blocks’ I/O Enabled LEDs go off frequently, 153.6 Kbaud extended should be used. The baud rate selected should be indicated on all blocks, especially if different busses in the facility use different baud rates. Before connecting a Hand-held Monitor (HHM) to a functioning bus, check that it has been configured to the correct baud rate. If not, change the HHM baud rate selection, turn off the HHM, connect it to the bus, then turn the HHM on.

Bus Length and Baud Rate for Busses with Phase A Devices

If a bus has any Phase A Genius products (catalog numbers IC660CBDnnn, IC660CBSnnn, IC660CBAnnn, IC660HHM500, or IC660CBB900/901), the bus must use 153.6 Kbaud “standard” and the maximum bus length is 2000 feet. Therefore, only the cable lengths listed under “153.6s" are permitted (“153.6e" refers to 153.6 Kbaud extended, which is not compatible with 153.6 Kbaud standard).

A - 4 PANELWARE MMI Application Manual for GE Fanuc Genius Protocol - June 1995 GFK-1115