GE 90-30 PLC Series Installation And Hardware Manual page 345

Serial Ports and Cables
Appendix
A
This appendix describes the serial port, converter, and cables used to connect Series 90 PLCs for
Series 90 Protocol (SNP). This information is included for reference and for those users who have
applications that require cable lengths different than the factory-supplied cables.
This appendix contains the following information:
RS-422 Interface
The Series 90 PLC family of products are compatible with EIA RS-422 specifications. RS-422
drivers and receivers are utilized to accomplish communications between several system
components using multiple driver/receiver combinations on a single cable with five twisted pairs.
The cable length between master and any slave cannot exceed 4,000 ( ,2 9 meters) feet.
A multi-drop system of eight drivers and receivers can be configured. The maximum common
mode voltage between each additional drop is the RS-422 standard of +7 Volts to -7 Volts. The
driver output must be capable of 2 V minimum into 00 ohms. The driver output impedance must
be at least 20 K ohms in the high impedance state. The receiver input resistance is 2 K ohms or
greater. Receiver sensitivity is 200 millivolt.
GFK-0356Q
Communications Interface
Cable and Connector Specifications
Serial Port Configuration
RS-232/RS-485 Converter (Catalog No. IC690ACC900)
Serial Cable Diagrams
Point-to-Point Connection
Multidrop Connection
Care must be taken that common mode voltage specifications are met.
Common mode conditions that exceed those specified will result in errors in
transmission and/or damage to Series 90 PLC components. When the
common mode voltage specification is exceeded, a port isolator such as the
IC690ACC903 must be used. See Appendix E for details on this port
isolator.
Caution
A-1