Technical information

Serial Solutions What To Do First
RS422 ports only have a transmitted data line pair, a
received data line pair, request to send output line pair and clear
to send input line pair.
Therefore the usual RS422 handshake is the RTS /CTS
handshake. Here the traffic light signal is passed out of the PC
to the external device on its RTS wire. The traffic light signal
from the external device is brought in on the PC’s CTS wire.
The PC will only transmit, ie send, data when the CTS
input is green, ie logically true. The PC will stop transmitting
data when the CTS input is red, ie logically false.
When the PC is able to receive data it will set the RTS
output green, ie logically true. When it cannot accept any data it
will set the RTS output red, ie logically false.
The RS422 RTS/CTS handshake is was passed to the
NEWCOM.SYS driver by the /Hr,1 parameter. Where r specifies
the COM ports, r may be a single port or a range of ports. For
example:-
/H1,1 sets up RTS/CTS handshaking for COM1.
/H12,1 sets up RTS/CTS handshaking for COM12.
/H7-16,1 sets up RTS/CTS handshaking for COM7 to COM16.
RS485 Handshake Lines.______________________
The RS485 interface is based in the RS422 standard but
have only one or two signals. As in RS422, to reduce noise
while allowing high speeds and long distance transmission each
signal is carried by two wires as a twisted pair, and is thus a
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