Basic Communication Protocol Descriptions - FreeFlight 2101 I/O Approach Plus Installation And Checkout Manual

APPENDIX B - Serial Interface Specification
B.1 INTRODUCTION
Serial communication capabilities for the FreeFlight 2101 I/O Approach Plus are provided by two bi-directional serial
communication ports compatible with EIA RS-232 and RS-422 protocols. Different formats may be selected on each port
providing the user flexibility in interfacing various systems with the FreeFlight 2101 I/O Approach Plus.
All information contained in this section is subject to change without notice.
B.2

BASIC COMMUNICATION PROTOCOL DESCRIPTIONS

B.2.1 RS-422
The RS-422 protocol uses differential signals with a magnitude in the range of 2-6 volts and a polarity as follows:
Logic 1: The non-inverting (+) signal is negative with respect to the inverting (-) signal (Signal Condition = MARK).
Logic 0: The non-inverting (+) signal is positive with respect to the inverting (-) signal (Signal Condition = SPACE).
RS-422 has the capability of driving up to ten receive devices in parallel from a single transmitter. It can drive long
cable lengths and has superior noise immunity.
B.2.2 RS-232
The RS-232 protocol specifies a bipolar, unbalanced signal referenced to a common ground (serial common). For
example, for RS-232D, the polarity is as follows:
Logic 1: The transmitter voltage is between -5V and -15V (Signal Condition = MARK).
Logic 0: The transmitter voltage is between +5V and +15V (Signal Condition = SPACE).
B.2.3 RS-423
The RS-423 protocol specifies a bipolar, unbalanced signal referenced only to the transmitter's ground and is
received differentially. The polarity is as follows:
Logic 1: The transmitter voltage is -4V to -6V (Signal Condition = MARK).
Logic 0: The transmitter voltage is +4V to +6V (Signal Condition = SPACE).
Revision E
May 31, 2006
FreeFlight 2101 I/O Approach Plus GPS Navigation System
Page B-1