This module is an interface converter from RS232 (standard PC COM port) to RS422 or RS485 (switchable) without galvanized separation. Noteworthy are its extreme flexibility, ease of use, and configurability for various operating situations.
The integrated 4-way DIP switch enables you to switch the terminating resistors for each data channel separately and to switch between RS422 and RS485 operation. There is also a special master control signal for RS485 operation.
Power can be supplied by various means and the module adjusts automatically as needed. For example, the module can simply be attached to the COM port for peer-to-peer operation, configured as an RS422 module (part of the standard package). In this instance, it draws power from the (active) handshake lines, assuming that these can deliver at least 10mA per output, which is generally the case. Two PCs configured in this way can be connected with a normal null modem cabel. Since they are operated with RS422, the cable can be significantly longer than in RS232 operation (RS485 operation is not possible in this configuration).
Flexible RS422/RS485 interface
Many host devices with RS232 interfaces offer the possibility (usually optional) to supply attached peripherals with +5 Volt via pin 9 on the Sub-D connector. This applies, for instance, to practically all taskit computer models. The module will automatically use this power supply, if available. In this configuration, and in the option that follows, RS485 is also supported.
As an additional variation, you can also supply +5Volt to +15Volt power from the RS422/RS485 side. Although supplied only at one point (e.g. the master), this power can then be used by each participant, as long as the required lines are available in the cable. This holds true in both RS422 peer-to-peer operation and in RS485 bus use.
A particularly intriguing feature of the RS232-TO-RS485 interface converter (going beyond the RS422/RS485 specification) is the switchable MCS (Master Control Signal). You can use this to implement power management controlled by the master device or also simply for a shorter reaction time from the slave (in RS485 operation).