1: Solution synopsis:
RS-422, RS-485 and RS-232 are dissimilar, the data signal uses
the difference transmission mode, also is called as the balance
transmission, it uses a for twisted pair line, definition is A,
another definition is B. In the usual situation, transmits
between driver A, the B level in +2~+6V, is a logical condition, the
negative level in -2V~6V, is another logical condition. And some
signal C, also has in RS-485 one "enables" the end, but this is may
use in RS-422 to be possible not to use. "Enables" the end is
uses in to control the transmission driver and transmission line
shutting off with the connection. When "enables" carries the
function, transmits the driver to be at the high anti- condition, is
called as "三", namely it does not have to the logic "1" and "0"
三.
Because RS-485 is, therefore RS-485 many electricities which
develops from the RS-422 foundation comes stipulated and RS-422 is
similar. If all uses the balance transmission mode, all needs to
meet 终接 the resistance in the transmission line and so on.
RS-485 may use two with four ways, the two-wire system may
realize the genuine multi- spots twp-way communication. The
RS-485 main line, when the request signal distance is several dozens
meters to on kilometer, widely uses the RS-485 serial main line
standard. RS-485 uses the balance transmission and the
difference receive, therefore has the ability which the suppression
altogether mold disturbs. Adds on the main line transceiver to
have the high sensitivity, can examine lowers to the 200mV voltage,
therefore the transmission signal can obtain the restoration outside
the kilometer. RS-485 selects the half-duplex work method, any
time only can have point is at the transmission condition, therefore,
transmits the electric circuit to have by to enable the signal to
perform to control. RS-485 uses in the multi- spots interlocks
when to be extremely convenient, may save many holding wires.
May the networking constitute the distributional system using
RS-485, its permission most parallel 32 driver and 32 receivers.
RS-485 and RS-422 different also lie in it altogether mold
output voltage is different, RS-485 is -7V to +12V between, but RS-422
in -7V to +7V between; RS-485 satisfies all RS-422 the standard,
therefore the RS-485 driver may use in the RS-422 network applies.
RS-485 and RS-422 are same, its maximum transmitting range
approximately is 1,219 meters, the maximum transmission speed is
10Mbps. The balanced twisted pair line length and the
transmission speed have the inverse ratio, below the 100Kbps speed,
only then possibly uses stipulates the longest electric cable length.
Only has under the very short distance can obtain the maximum
speed transmission. The common 100 meter long twisted pair lines
maximum transmission speed is only 1Mbps.
Because the RS-485 standard appears time comparison early,
although this kind of standard now still generally applied in the
industrial automation, places the monitoring, the data acquisition,
and so on many domains, but it also had its congenital flaw, that was
its electrical standard limit, caused the RS-485 signal only to be
able to carry on the host, inquires the way communication from the
structure wheel, communication timeliness and the reliability slightly
misses. Meanwhile in RS-485 network, when the system has the
mistake, when appears at the same time the multi- pitch points to the
main line transmission data, causes the main line to present
short-circuits, thus damages certain pitch points the phenomenon.
Although RS-485 also is the main line system communication way,
but its communication is away from also only forms the signal about
1,200 meters the weaken, in the usual situation, the system needs
moreover to serially connect RS-485 the photoelectricity isolation
repeater to make the signal to enlarge, if the distance is farther,
then the RS-485 repeater needs to like "the baton" to be same, in each
RS-485 signal attenuation place, installs the RS-485 light to separate
the repeater to solve the signalling problem. But this kind of
solution has an important question to need to solve, because has not
added RS-485 the photoelectricity isolation repeater, then all needs
to receive a telegram in the string to the repeater writes down with
the external power supply which actuates. But in various
application, certainly is not each weaken spot has the possibility to
facilitate turns on the power source (for instance in coal mine mine
shaft system). Based on this present situation, can have the
user to use the optical fiber communication the way. But this
plan obviously has the wiring to be expensive, interface equipment
usual price also quite high question.
The our company according to the customer the demand, now
provided RS-485 in to the twisted pair line to take the communication
medium, under the half-duplex communication, the low gear rate
pattern, was allowed to transmit the RS-485 signal 10 kilometer within
the solution, product is called RS-485 Short Haul Modem. This
plan not only may solve the RS-485 point-to-point communication,
moreover also may compose has the pitch point the main line system
structure, this communication way and usual RS-485 main line similar,
each hangs in the network has RS-485 Short Haul Modem the RS-485
interface equipment, even hangs meets the RS-232 Short Haul Modem
RS-232 equipment which the our company produces, may control the
computer with on host the way communication which to the wheel
inquires.
In order to guarantee the network the security, the our company
provides RS-485 Short Haul Modem is the industry level standard
design, not merely is the signal photoelectricity isolation, moreover
the power source also is the DC-DC isolation transforms, and has anti-
is struck by lightning the primary device to use to make 突波 the
protection. The our company produces RS-485 Short Haul Modem and
RS-232 Short Haul Modem, its core principle is transforms into RS-485
perhaps the RS-232 level CAN (Controller Area Network) the main line
level, far-end RS-485 Short Haul Modem or RS-232 Short Haul Modem,
again transforms into the RS-485 level or the RS-232 level by the CAN
level, thus has completed RS-485 perhaps the RS-232 signal ultra
long-distance transmission. Because well known, the CAN main
line has the prominent reliability, timeliness and the flexibility.
The CAN main line passes CAN controller connection chip 82C250
two out-ports CANH and CANL and the physical main line is connected,
but the CANH end condition only can be the high level or the suspended
state, the CANL end only can be the low level or the suspended state.
This guarantee cannot leave the phenomenon in the RS-485
network, when the system has the mistake, when appears at the same
time the multi- pitch points to the main line transmission data,
causes the main line to present short-circuits, thus damages certain
pitch points the phenomenon. Moreover the CAN pitch point has
the automatic shut-off output function in the wrong serious situation,
causes on the main line other pitch points operations not to receive
affects, thus guaranteed cannot leave the phenomenon in the network,
because the individual pitch point has the problem, causes the main
line to be at "the deadbolt lock" the condition. Therefore
selects this method to solve the RS-232/485 ultra long-distance range
communication, does not lose is one kind stable, is reliable moreover
the economical solution. In in the RS-485 very-long-range
solution, stable is reliable and the low power loss characteristic as
a result of its product performance, already batch application in coal
mine mine shaft checking attendance supervisory system. Customer
RS-485 Short Haul which produces the our company the Modem seal in it
tallies in this peaceful authentication control box, in is away from
in 3000-6000 meter scope, by the 9600BPS communication speed under,
has completed in the coal mine mine shaft monitoring equipment and the
well monitors the main engine the RS-485 communication. After
the actual movement, the communication extremely stable is reliable.
2: Application graphical representation
A:) Application way one: Point-to-point
communication B:) To multi- spots main line system application
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Jinan Pu news science and technology limited liability
company
Sale department: Li Min
Telephone: 0531-846424518 86.652206 million
Facsimile: 0531-86424519
Electricity postal: Limin@pxtech.cn
Website www.pxtech.cn
Jinan Puxun Technologies.Co., Ltd
No.5-1 Yangtouyu Street Jinan Shandong
Province.P.R.China
Sales Manager: Mr.Li Min
Tel:+86-531-86424518 86.652206 million
Fax:+86-531-86424519
E-mail: Limin@pxtech.cn
MSN:puxuntech@hotmail.com
Skype:pxtech2
Web:www.linkports.com
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