1: Solution synopsis:
The serial communication interface standard after the use and
the development, at present already had several kinds. But all
is the process changes in the RS-232 standard foundation then forms.
Therefore, primarily discusses by RS-232C. The
correspondence agreement together which the RS-323C standard is
American EIA (the electronics industry federation) which with company
and so on BELL develops in 1969 announces. It suits to the data
transmission speed in 0 ~ 20000b/s scope correspondence. This
standard to the serial communication connection related question, like
the holding wire function, the electric appliance characteristic all
did had explicitly stipulated. Because the general equipment
merchant all produces and the RS-232C service pattern compatible
communication facility, therefore, it takes one kind of standard, at
present already in microcomputer correspondence connection widespread
use.
In AT machine and after, does not support the 20mA electric
current link connection, uses the DB-9 coupling, the achievement
provides on the multi-purpose I/O card or the motherboard COM1 and the
COM2 two serial interfaces couplings. It only provides the
asynchronous communication 9 signals. The DB-25 coupling pin
assignment and the DB-25 pin signal is completely different.
Therefore, if with matches meets DB-25 the coupling the DCE
equipment connection, must use the special electric cable line.
Electric cable length: Is lower than 20kb/s when the
correspondence speed, the RS-232C direct connection maximum physical
distance is 15m (50 feet). The maximum direct transmission
distance explained that, RS-232C standing operating procedure,
if does not use MODEM, is smaller than in 4% situation in the element
distortion, between DTE and DCE the maximum transmitting range is 15m
(50 feet). Obviously this maximum distance is smaller than
under 4% premise in the element distortion to produce. In order
to guarantee the element distortion is smaller than 4% request, the
interface standard stipulated in the electrical specification, the
driver load electric capacity should be smaller than 2500pF.
Because the RS-232 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 its congenital flaw also extremely was
actually obvious, that was its electrical standard limit, caused the
RS-232 signal not to be able to carry on the long distance the
communication, moreover a flaw was the RS-232 connection very easily
because of factor and so on surge, return route voltage, the merely 10
several volts voltages undulations, possibly caused the connection
chip the damage. Based on this present situation, the domestic
and foreign very many companies all develop RS-232 the
photoelectricity isolation long-line driver, this kind of product can
satisfy RS-232 in 1,000 meter about signal entire duplex
point-to-point (Point to Point) the communication, moreover beginnings
and ends mutually photoelectricity isolation.
But this kind of plan also has not not perfectly place, that is
by the twisted pair line took under the transmission line cable medium
condition, is unable to complete the long-distance range
communication, the long-distance range communication, only can depend
on the expensive optical fiber communication to solve this need, 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-232 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-232 signal 10 kilometer within
the solution, product is called RS-232 Short Haul Modem. This
plan not only may solve the RS-232 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-232 Short Haul Modem the RS-232
interface equipment, even hangs meets the RS-485 Short Haul Modem
RS-485 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-232 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-232 Short Haul Modem and
RS-485 Short Haul Modem, its core principle is transforms into RS-232
perhaps the RS-485 level CAN (Controller Area Network) the main line
level, far-end RS-232 Short Haul Modem and RS-485 Short Haul Modem,
again transforms into the RS-232 level or the RS-485 level by the CAN
level, thus has completed RS-232 perhaps the RS-485 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-232 very-long-range
solution, stable is reliable as a result of its product performance,
has been massively used by the domestic war industry unit, displays
splendidly in the practical 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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