Acromag IOS-521 Series, Руководство пользователя

Страница: 20 / 21

S
E
RIE
S
IO
S
-52
1 I
/O
S
E
RV
E
R MO
DULE
E
IA
/T
IA
-42
2B
S
E
RIA
L CO
MM
UNICAT
IO
N MO
DULE
_______________
___________________________________________________________________________
- 20
-
RB
RT
RB
Rx D+
RB +VB
Tx D-
Tx D+
Rx D
Tx D
RB
-VB
RT
RB
R
x
D
+
R
x
D
-
T
x
D
+
T
x
D
-
RB
RT
RT
Rx D-
Tx D+
Rx D-
Rx D+
+VB RB
Rx D
Tx D
-VB
RT
RB
R
x
D
T
x
D
Tx D-
Tx D-
Tx D+
+VB
-VB
UNIT 1 ( DTE)
Rx D_ENABLE
Rx D
Tx D
Rx D
UNIT 1 ( DTE)
Tx D_ENABLE
Rx D_ENABLE
Tx D
Rx D-
Rx D+
Tx D+
+VB
Rx D-
Rx D+
-VB
UNIT N ( DCE)
UNIT 2 ( DCE)
Tx D_ENABLE
Tx D-
T
x
D
_
E
N
A
B
L
E
UNIT I
( DCE)
R
x
D
_
E
N
A
B
L
E
RS422/RS485 FULL DUPLEX (MULTIDROP NETWORK)
Rx D_ENABLE
Tx D_ENABLE
IOS-521 RS-422/485 INTERFACE DIAGRAM
RS422 FULL DUPLEX (TWO NODE NETWORK)
Tx D_ENABLE
Rx D_ENABLE
1. FOR A N RS 422 NE TWORK , INS TA LL A TE RMINA TING RE S IS TOR A T THE
RE CE IV ING E ND OF THE NE TWORK ONLY
5. THE IDLE S TA TE OF THE TxD & RxD DA TA P A IRS A RE HIGH ON TxD+
& RxD+. THIS CORRE S P ONDS TO A MA RK (1) ON THE DA TA LINE .
NOTE S CONCE RNING RE S IS TOR P LA CE ME NT A ND RE MOV A L FOR RT A ND RB :
4. THE TxD LINE S OURCE D FROM A P ORT CA N B E P E RMA NE NTLY E NA B LE D
V IA S OFTWA RE . IF S O, THE NE TWORK B IA S RE S IS TORS A S S OCIA TE D WITH
E A CH P A IR OF S IGNA L WIRE S WILL NOT B E NE E DE D. THE S E RE S IS TORS
A RE INS TA LLE D IN S OCK E TS A ND CA N B E RE MOV E D IF THE S E DRIV E RS A RE
A LWA Y S E NA B LE D.
6. RS -422 IS CONS IDE RE D A B A LA NCE D (DIFFE RE NTIA L) TRA NS MIS S ION
S TA NDA RD B E CA US E THE V OLTA GE OF ONE S IGNA L LINE IS TA K E N
WITH RE S P E CT TO A NOTHE R TO DE TE RMINE THE S IGNA L LE V E L.
2. A LL RS 422/RS 485 TRA NS MITTING A ND RE CE IV ING CHA NNE LS MA Y HA V E
TE RMINA TING RE S IS TORS (RT) A T B OTH E NDS OF THE NE TWORK . THE
IOS -521 HA S THE S E RE S IS TORS (120 OHM) INS TA LLE D IN S OCK E TS A ND THE Y
MA Y B E RE MOV E D A S RE QUIRE D.
3. THE RE MUS T B E A T MOS T, ONE S E T OF B IA S RE S IS TORS A S S OCIA TE D
WITH E A CH P A IR OF S IGNA L WIRE S TO K E E P THE NE TWORK FROM
FLOA TING WHE N NO UNITS A RE TRA NS MITTING.