Switched & Unswitched Modes; Switched Mode - Emerson ControlWave GFC IStran Instruction Manual

2.2 Switched & Unswitched Modes
Issued Nov-09
ControlWave GFC IS Communication Interface Manual (CI-CW-GFC-ISTRAN)
You can configure each IStran interface independently to operate in
switched or unswitched mode. In switched mode, the TX drivers can
enter a high-impedance state to reduce power consumption. The outputs
transition smoothly to and from the high-impedance state. Most modern
device inputs pull the high impedance IStran output to ground and
interpret it as a low, or mark state. Some devices may not properly
interpret the high-impedance signal, and in some systems it is
impractical for you to operate either or both interfaces in switched
mode. In these cases, or when power consumption is not a concern,
configure the interface(s) for unswitched mode. In unswitched mode,
the TX drivers are always active and they always follow the
corresponding RX inputs.
You enable or disable switched mode for the hazardous interface by
jumper position HJP1, and for the non-hazardous interface by jumper
position NJP1 (see Figures 2-1 and 2-2). When either interface is in
switched mode, the RX3 (NRX3 or HRX3) input of the opposite
interface turns it on or off.
Function and Electrical Characteristics
Figure 2-2. Setting Jumper NJP1
2-5