Technical information

Serial Solutions What To Do First
type 3. The RS485 transmit only handshake is passed to the
NEWCOM.SYS driver by the /Hr,3 parameter. Where r is the
COM port number, r may be a single port or a range of ports.
For example:-
/H1,3 sets up 485 transmit only handshaking for COM1.
/H12,3 sets up 485 transmit only handshake for COM12.
/H7-16,3 sets 485 transmit only handshake for COM7 to
COM16.
RS485: Party Line Half Duplex. One cable.
The RS485 party line, half duplex handshake connects one
PC to one or mode devices using only ONE twisted pair cable.
The devices, including the PC, take turns to transmit data along
the cable, all can receive the data transmitted. The PC usually is
the master controlling the other devices. Each device has its own
address and only transmits data when the master commands it to
do so. When the PC is not actually in the process of transmitting
data, it removes its own transmitters from the bus so allowing
the devices to transmit their information down the common
twisted pair.
The RS485 party line, half duplex handshake is was passed
to the NEWCOM.SYS driver by the /Hr,2 parameter. Where r is
the COM port number, r may be a single port or a range of
ports. For example:-
/H1,2 sets up 485 half duplex handshaking for COM1.
/H12,2 sets up 485 half duplex handshaking for COM12.
/H7-16,2 sets 485 half duplex handshaking for COM7 to
COM16.
RS485: Party Line Full Duplex. Two cables.
The party line full duplex connects a PC to one or more
devices using two twisted pair cable. The transmit of the PC
goes to the receive input of all the devices, the transmit of the
devices is joined together and goes to the receive input of the
PC. The PC can transmit data whenever it wishes, even when
the devices are transmitting data. The devices take turns to
transmit data along the cable. The PC is the master controlling
the other devices. Each device has its own address and only
Page 16 Chapter 1