Renu Electronics GWY-800 Series, Руководство пользователя

Страница: 32 / 35

Appendix
28
Doc No: UMAN\GWY-300-B\0106
REVISION 0
3. “Burst” is an optional communication mode (Figure 5), which allows a single slave device to continuously
broadcast a standard HART, reply message. This mode frees the master from having to send repeated command
requests to get updated process variable information.
The same HART reply message (PV or other) is continuously broadcast by the slave until the master instructs the
slave to do otherwise. Data update rates of 3-4 per second are typical with “burst” mode communication and will
vary with the
chosen command. Burst mode should be used only in single slave device networks.
4. The HART protocol also has the capability to connect multiple field devices on the same pair of wires in a
multi-drop network configuration as shown in Figure 6. In multi-drop applications, communication is limited to
master/slave digital only. The current through each slave device is fixed at a minimum value to power the device
(typically 4 mA) and no longer has any meaning relative to the process.