3.1.
(..1.2):
- ;
- ();
- .
- , , . , . , , , . , .
, . , , 1-2 . , . :
( , );
, , , .
, , , . , .. , , . . , , . , , , 17 . . , . , 1-2 , .
, : . . , , . , () .
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, , () . , ( ) .
() . , , . , , , . , , . , , , . . , , , , , ( ) (shared media ). , .
(star) , , , master (). (), , slave (). , .
, (ring), , (master) , . , (token), . , , : Token Ring ( ).
, (bus), . , , , - , . , (master), .. , . , , , .
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, CSMA/CD (Carrier Sense Multiple Access with Collision Detection). Ethernet. , . , , . , , . , , , , , . , , . , , . . , , . , . , , .
CSMA/CD - , . , , , . CSMA/CD ( 30 %), .
, OSI (Open Systems Interconnection) , (ISO). 1-,2- 7- OSI, .. , .
(Physical Layer) . , ( , , .). , , , .
(Data Link Layer) , (frames). , . : Modbus, Profibus, Ethernet, Token Ring, FDDI ( ) .
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(Application Layer) .
, , . , OSI, . OSI, .
3.2. RS232C RS485
RS232C RS485 (RS Recommended Standard). EIA (Electronics Industries Alliance). RS232C PtP (Point-to-Point -). RS232 COM-(Communication Port) . RS232C PtP, . RS232C , 3.1.
3.1. RS232C
SG(Signal Ground) | |
TD(Transmitted Data) | , |
RD(Received Data) | , |
DTR(Data Terminal Ready) | |
DSR(Data Set Ready) | |
RTS(Request To Send) | |
CTS(Clear To Send) |
3.1 RS232C TD SG, RD SG. , , .. .
RS232C DTR=1, . DSR=1, RTS=1 CTS=1 . , . . , , . , . , . ( ) .
RS232C 115,2 / 15 , . ( ), , . , , , . .
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RS485, RS232 (). , RS485, . 3.1. RS485 : G R. (G) . G TD, G RS232. (U), U. , , . R , U, , RD. , . 3.1, : SG ( ). 10 / 15 90/ 1200 . 32 - .
.3.1. RS485
120 . RS485 .
. 3.1 , , . , G ( R) : , . G RTS=1, RS485 R (. .3.1). RTS=0 G RS485 , R . , RS485, , . , , R. , U, RD, RS 232 , . G .
RS485. , . RS232/RS485 , 32 (.3.2). . (repeater) RS485 , , , . 32 .
. 3.2. RS485 -
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, RS485, .3.2, USB, USB/RS485. USB ( 12/ 5 ), .
3.3.
.3.3. ( 1) () , , . , . , , (). , , , , . , . (). , . , , .
, . (), , . , . 3.3, Ethernet ( ). Ethernet . ( 2) Ethernet, Profibus, Canbus .
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. 3.3.
, Fieldbus ( ). 4-20 0-10 . , - , , . , , . Fieldbus Profibus SIEMENS () Modbus MODICON ().
4