** 1 ** RS-485 Txheej txheem cej luam
Zoo li RS-232, RS-485 yog tus qauv sib txuas lus sib txuas. Nws txoj kev xaiv tam sim no yog TIA-485 / EIA-485-A, tab sis nws feem ntau hu ua RS-485 tus qauv. RS-485 yog siv dav hauv kev lag luam xws li kev lag luam automation, tsheb, thiab kev tswj vaj tsev. Nyob rau hauv cov qauv EIA series, RS-485 raws tu qauv yog suav hais tias yog ntau yam, ua tau zoo tshaj plaws nyob rau hauv tag nrho plaub serial kev sib txuas lus qauv.
RS-485 tsheb npav kov yeej qhov tsis txaus ntawm RS-232-npe, nws qhov kev sib txuas lus luv luv thiab cov ntaub ntawv tsawg. RS-485 txhawb cov ntaub ntawv tus nqi txog li 10 Mbit / s thiab muaj kev sib txuas lus theoretical txog li 1,200 meters. Tsis zoo li kev sib kis ib leeg ntawm RS-232, RS-485 siv qhov sib txawv ntawm kev sib kis ntawm ib khub ntawm cov xov hlau sib tw, nrog rau ib lub xaim raws li A thiab lwm yam li B.
** 2 ** RS-485 Lub cev txheej
Lub RS-485 lub cev txheej yog lub luag haujlwm rau kev xa cov ntaub ntawv nyoos ntawm cov khoom siv thiab lub cev sib kis nruab nrab. Nws tswj cov kev hloov pauv ntawm cov teeb liab hluav taws xob rau cov ntaub ntawv digital, thaum tseem txhais cov qib voltage, lub sijhawm, cov ntaub ntawv tus nqi, thiab lwm yam tsis.
① Cov teeb liab sib txawv
Ntev -kab kab nyob deb ua rau lub teeb liab attenuation thiab ua rau kom muaj suab nrov thiab cuam tshuam. Qhov no tshwm sim raws li kev hloov pauv ntawm qhov hluav taws xob amplitude ntawm cables A thiab B. Txawm li cas los xij, qhov zoo ntawm kev siv cov kab sib txawv yog tias rho tawm qhov sib txawv ntawm ob lub teeb liab tshem tawm qhov cuam tshuam, tso cai rau lub teeb liab ib txwm tso tawm. Lub peev xwm ntawm tus neeg txais kev sib txawv kom tsis quav ntsej qhov sib npaug ntawm ob lub teeb liab kab yog hu ua ntau- hom kev tsis lees paub.
Tus qauv qhia tias logic 1 yog +2V rau +6V, thiab logic 0 yog -6V rau -2V.
RS-485 tsis xav tau ib lub tsheb npav tshwj xeeb; nws tsuas yog txiav txim siab qhov tsawg kawg nkaus qhov sib txawv voltage. Tshaj qhov ntev cable ntev, qhov hluav taws xob tau txais los ntawm tus txais yuav poob mus rau +/- 200 mV, uas tseem zoo kawg nkaus rau RS-485-qhov no yog ib qho zoo ntawm RS-485.
Ntau lub transceivers tau ntsib lossis tseem dhau TIA / EIA-485A tus qauv; Txawm li cas los xij, hauv cov ntawv thov siv tau, txawm li cas los xij, cov cuab yeej tau teev tseg ua ntej. Piv txwv li, qhov tsawg kawg nkaus tsis zoo cov tswv yim pib rau ib qho transceiver yog -200 mV.
② Cov lus txhais
RS-485 Cov Lus Qhia Kab Lus Txhais
Schematic Daim duab ntawm DB9 Txiv neej thiab poj niam Connectors
| DB 9 | Ring Indicator | Pin npe |
|
1 |
CD | Carrier Detect |
| 2 | RXD | Txais Cov Ntaub Ntawv |
| 3 | TXD | Xa cov ntaub ntawv |
| 4 | DTR | Cov ntaub ntawv Terminal Npaj |
| 5 | GND | Qhov System Av |
| 6 | DSR | Cov ntaub ntawv npaj |
| 7 | RTS | Xa lus thov |
| 8 | CTS | Ntshiab rau Transmit |
| 9 | RI | Ring Indicator |
DB9 Pin Assignment
Carrier Detect (CD) Cov teeb liab tswj xyuas no yog siv thaum lub modem ceeb toom rau lub computer tias nws tau kuaj pom lub teeb liab uas lub computer siv tau rau kev xa cov ntaub ntawv.
Txais Cov Ntaub Ntawv (RXD) Cov kab no yog siv rau kev xa cov ntaub ntawv ntawm ob qhov chaw. Ib qho piv txwv yog cov ntaub ntawv tau txais los ntawm modem thiab xa mus rau lub computer.
Transmit Data (TXD) Qhov no yog kab uas ua tau cov ntaub ntawv xa mus.
Cov ntaub ntawv Terminal Ready (DTR) Cov teeb liab no qhia tias lub khoos phis tawj tau npaj xa cov ntaub ntawv.
System Ground (GND) Hais txog kev sib txuas ntawm lub cev mus rau hauv av, siv los ntsuas qhov ntsuas hluav taws xob hauv Circuit Court lossis ua ib txoj hauv kev rau rov qab tam sim no.
Pinout Diagram rau 25-Pin RS-485 Ib Nrab-Duplex thiab Full-Duplex Connectors
Piv nrog rau DTR teeb liab, Cov Ntaub Ntawv Npaj Npaj (DSR) teeb liab ceeb toom rau lub computer lossis lub davhlau ya nyob twg tias lub modem ua haujlwm thiab muaj peev xwm tau txais cov ntaub ntawv.
Rau cov teeb liab no, yuav tsum muaj qhov hluav taws xob zoo los pab kom npaj xa (RTS) teeb liab. Qhov no qhia tau hais tias kev cuam tshuam - kis tau dawb yog ua tau ntawm cov ntaub ntawv teev thiab cov ntaub ntawv davhlau ya nyob twg.
Tom qab kev sib txuas yog tsim los ntawm cov ntaub ntawv davhlau ya nyob twg thiab lub modem, lub teeb liab Clear to Send (CTS) tau xa mus kom paub meej tias cov ntaub ntawv davhlau ya nyob twg tau lees paub tias kev sib txuas lus tuaj yeem pib.
Lub Nplhaib Qhov Ntsuas (RI) ua haujlwm ceeb toom rau lub modem ua haujlwm cov ntaub ntawv teeb tsa uas tsis tshua muaj -frequency signal tau raug kuaj pom. Qhov teeb liab no tsuas yog ceeb toom cov ntaub ntawv davhlau ya nyob twg thiab tsis cuam tshuam cov ntaub ntawv xa mus ntawm cov khoom siv.
Pin assignments txuas rau DB9 thiab DB25 connectors ntawm 2 thiab 4 hu, feem.
TxD+ thiab TxD- kab ntawm DB25 connector xa cov ntaub ntawv, thaum RxD+ thiab RxD- kab nqa tau txais cov ntaub ntawv. Vim tias cov no yog cov cim sib txawv, lawv tuaj yeem kis tau mus ntev dua.
RS-485 interface ua tau zoo tshaj RS-232 raws tu qauv ntawm kev sib kis nrug thiab cov ntaub ntawv tus nqi. Nws txhawb cov ntaub ntawv tus nqi ntawm 30-35 Mbps nyob deb li ntawm 10 meters. Cov ntaub ntawv tus nqi ntawm 100 Kbps tuaj yeem ua tiav qhov kev ncua deb txog li 1,200 meters. RS-485 feem ntau yog siv nyob rau hauv multipoint configurations uas coj kom zoo dua ntawm nws balanced sib txawv interface.
Raws li pom nyob rau hauv RS-485 cable pinout, qhov no interface nta tag nrho cov teeb liab nyob rau hauv ib tug txawv configuration.
● Cov CTS+ thiab CTS- cov cim, nrog rau RTS+ thiab RTS- cov cim, yog siv los tuav tes tswj cov cim.
● TxD+ thiab TxD- yog siv rau kev xa cov ntaub ntawv.
● RxD+ thiab RxD- yog cov kab siv los txais cov ntaub ntawv.
Ib tug multipoint configuration tuaj yeem txuas mus txog 32 cov khoom siv rau ib qho khoom siv tswj hwm. VSAT NMS (Network Management System) yog ib qho piv txwv zoo li no. Hauv qhov kev siv no, software khiav ntawm lub PC tuaj yeem saib xyuas thiab tswj ntau lub subsystems. Cov no suav nrog MUX, modem, RF up/down converters, thiab lwm yam network Cheebtsam. Rau hom kev siv no kom ua haujlwm tau zoo, raug xaim RS-485 connectors yog xav tau ntawm ob lub PC uas khiav NMS daim ntawv thov thiab tag nrho cov subsystems txuas.
RS485 Interface piav qhia
Lub RS485 (EIA485) interface tau ua pov thawj tias muaj zog heev thiab, vim nws qhov ntau -point topology, tau dhau los ua kev sib txuas lus nrov tshaj plaws hauv kev lag luam. RS422 raws tu qauv zoo ib yam li RS485 nyob rau hauv uas ob leeg siv cov teeb liab sib txawv rau cov ntaub ntawv xa mus.
Muaj ob hom RS-485:
● Ib nrab -duplex RS-485 muaj 2 tus pins.
● Tag nrho -duplex RS-485 muaj 4 tus pins.
Koj tuaj yeem siv tag nrho -duplex hom thaum koj xav tau xa thiab txais cov ntaub ntawv ib txhij. Hauv ib nrab- hom duplex, koj tsuas tuaj yeem xa lossis tau txais cov ntaub ntawv thaum twg los tau.
Qhov voltage ntau ntawm kab yog -7 V rau +12 V.
Tsis muaj ib hom kev sib txuas tshwj xeeb uas yuav tsum tau ua raws li RS-485 raws tu qauv, tab sis feem ntau, DB9 connectors lossis terminal blocks yog siv.
Tshwj xeeb RS-485 connectors yuav muaj ntau tus pin configurations. Koj tuaj yeem txiav txim siab qhov kev teeb tsa tiag tiag raws li cov ntaub ntawv muab nrog lub cuab yeej.
Txuas ib qho RS-485 Ntaus nrog 2 Pins-Half-Duplex RS-485 Pin Allocation
Txuas ib qho RS-485 Ntaus nrog 4 Pins-Full-Duplex RS-485 Pin Allocation
Ntau RS-485 converters niaj hnub no tau sib xws nrog RS-422, yog li koj feem ntau yuav pom cov cim npe T / R + thiab T / R- ntawm cov converters, uas sib haum rau RS-485's A + thiab B-.
③ Topology
RS-485 txhawb nqa ob-hlau thiab plaub-hloov teeb tsa. Plaub -hloov teeb tsa yog txwv rau taw tes- rau- taw tes kev sib txuas lus thiab tsis tshua siv niaj hnub no; ob-xaim configuration yog siv ntau dua. Qhov kev teeb tsa no siv lub tsheb npav topology, tso cai rau 32 qhov sib txuas ntawm ib lub npav.
Zoo li I²C, RS-485 tsheb npav ua haujlwm hauv tus tswv- hom qhev. Nws txhawb ob qho tib si taw tes-rau- taw tes ib leeg- qhev hom thiab ntau- qhev hom, tab sis tsis txhawb ntau hom tswv.
