Documentation Number: ESP902-2303 Manual
Chapter 2
13
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd – Westlink Commercial Park – Oranmore, Galway, Ireland – Ph +353 91-792444 – Fax +353 91-792445
RS-485 Connections
Some RS-485 devices are marked opposite from the RS-485 standard which
defines the Data B line as positive relative to Data A during a Mark state
before enabling the transmitter, and after transmitting before tri-stating. If the
RS-485 devices don’t respond, try swapping the Data B and Data A lines.
If you want to connect 4-Wire RS-485 devices, you can use the RS-422 Mode
provided that the ESP902 will be connected as a Master in a single master
system. If you have multiple masters, you cannot use this device, it does not
tri-state the transmitter in RS-422 mode.
