Omega Vehicle Security ISA RS-422 - Manual (Page 10)

Card Setup
OMG-ULTRA-SIO Page 6
Headers E8 (Port 1) and E10 (Port 2) are used to control the RS-485 mode
functions for the driver circuit. The two selections are ‘RTS’ enable or ‘Auto’
enable. The ‘Auto’ enable feature automatically enables/disables the RS-485
interface. The ‘RTS’ mode uses the ‘RTS’ modem control signal to enable the
RS-485 interface and provides backward compatibility with existing software
products. If you have E3 and E9 in the RS-422 mode and wish to have the RTS
signal present at the DB connector place a jumper over the RTS pins at E8 and
E10. Otherwise the RTS control signal will not be present at the DB connector.
Headers E3 (Port 1) and E9 (Port 2) are used to control the RS-485 enable/disable
functions for the receiver circuit and determine the state of the RS-422/485 driver.
The RS-485 ‘Echo’ is the result of connecting the receiver inputs to the
transmitter outputs. Every time a character is transmitted; it is also received. This
can be beneficial if the software can handle echoing (i.e. using received
characters to throttle the transmitter) or it can confuse the system if the software
does not. These header blocks are described in the illustration and table that
follow:
Echo
No
Echo 422 485
E3 = Port 1
E9 = Port 2
1
Position 1 ‘Echo’ Echoes the data that is transmitted.
All characters transmitted are
received. (Only relevant in the two
wire RS-485 Mode)
Position 2 ‘No Echo’ Inhibits the data that has been
transmitted. Receiver is off when
transmitter is on. (Only relevant in
the two wire RS-485 Mode)
Position 3 ‘422’ RS-422/485 Driver always enabled
(RS-422 Mode). RTS modem control
signal available on DB-9 connector.
Position 4 ‘485’ RS-422/485 Driver enabled by RTS
or ‘Auto’ enabled. Modem control
signal not available on DB-9
connector.