Specifications

Getting Started 1-3
RS-485 Quick Hook-up to a RS-232 port
An RS-485 module may be easily interfaced to an RS-232C terminal for
evaluation purposes. This connection is only suitable for benchtop operation
and should never be used for a permanent installation. Figure 1.3 shows the
hook-up. This connection will work provided the RS-232C transmit output is
current limited to less than 50mA and the RS-232C receive threshold is
greater than 0V. All terminals that use 1488 and 1489 style interface IC’s will
satisfy this requirement. With this connection, characters generated by the
terminal will be echoed back. To avoid double characters, the local echo on
the terminal should be turned off.
If the current limiting capability of the RS-232C output is uncertain, insert a
100Ω to 1kΩ resistor in series with the RS-232 output.
In some rare cases it may be necessary to connect the module’s DATA
pin to ground through a 100Ω to 1kΩ resistor.
Figure 1.2 RS-485 Quick Hook-Up.