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Why use a Technman Control-it Automatic Converter? |
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Traditionally, the RS232 serial interface protocol is the only connection
standard that has been adhered to by all computer manufacturers. However
RS232 is only able
to operate effectively where the computer and a single device connected
to it are situated within a few metres of each other.
Where information needs to be transmitted between multiple devices at
distances of up to 1.2 kilometres remote from the computer, the RS485
protocol is able to achieve this economically using a 2 wire 'twisted
pair' circuit. Technman's converters easily and economically provide
the interface between your computer's RS232 port and the RS485 system.
The RS485 communications protocol operates like a telephone party line. One
device communicates at a time. The Control-it 5001 and 5007 converter
are designed to enhance your data throughput up to 80% over similar converters.
Technman's automatic converters can do this because they have a very fast turnaround
time. Alternatively, the Technman Control-it
5006 gives you seamless communication in both directions simultaneously
(using a 4 wire system).
The 5001 and the 5007 are called "Automatic"
converters because they automatically detect the character being sent to
them and enable communication
the appropriate
direction. In contrast, manual converters require the user to tell them when
the RS232 device is transmitting
by raising the RTS line. By using an automatic converter, you are ensured that
your current software will continue to work.
The following screen shots compare a character sent at 9600 bps, showing
a conventional automatic converter versus the Control-it converter:
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Fig. 1 A standard converter
Total time wasted is 1300uSec
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Fig.2 The Control-it 5007 converter
Time wasted is less than 200uSec
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Figures 1 and 2 show the RS485 signal.
- To the left of point 'A', the RS485 line is floating and available
to any unit on the line.
- Between points 'A' and 'B' a single data character is being transmitted.
- Between points 'B' and 'C' the party line is being held without any
transmission taking place. This represents wasted time as no other
unit can transmit without data being lost, even though the line not
being utilised. Note that in Fig 2 this time has been reduced to less
than 200uSec.
- To the right of 'C' the RS485 line is once again floating and available
to any unit on the line to use.
The danger with a standard converter's wasted 1300uSec is that a remote
device will respond before the RS485 line is available. Some remote devices
can be programmed to wait longer before they respond, but this slows down
the data transfer. This
potential problem is eliminated with the Control-it converter, making
setup and operation simpler and faster.
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