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COM2 - RS- 422
J13
3 2 1
o o o
VCC
R29
R31
R32
Important Note: All serial termination components are surface mount 0805 packages. These
should only be installed by surface mount qualified individuals.
2.10.2
RS- 485 Mode Con figu ra tion
The RS- 485 Multi- drop in ter face is sup ported on both chan nels with the in stal la tion of the op tional
"Chip Kit", WinSystems' part number CK- 75176-2. A sin gle kit is suf fi cient to con fig ure both
chan nels for RS- 485. RS- 485 is a 2- wire multi- drop in ter face where only one sta tion at a time talks
(trans mits) while all oth ers lis ten (re ceive). RS- 485 usu ally re quires the twisted pair be ter mi nated at
each end of the run. The re quired ter mi na tion val ues are de pend ent upon a number of fac tors in clud ing:
line im ped ance, line length, etc. A good trial value is 100 ohms in all three re sis tor lo ca tions. The
fol low ing il lus tra tions show the cor rect jump er ing, driver IC in stal la tion, I/O con nec tor pin out, and
ter mi na tion re sis tor lo ca tions for each of the chan nels when used in RS- 485 mode.
030530
WinSystems - "The Embedded Authority"
J14
U28 - Not In stalled
U29 - In stalled
1 2 3
U30 - In stalled
o o o
RX+
TX-
EBC-LP OPERATIONS MANUAL
TX+
GND
RS- 422 NOTE: When used in RS- 422 mode,
the trans mit ter must be en abled by set ting the RTS
bit in the Mo dem Con trol Reg is ter (Bit1).
COM2 DB9
RX+
1 o o 6
N/C
RX-
2 o o 7
N/C
3 o o 8
TX-
N/C
4 o o 9
N/C
5 o
Page 2-9
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