WinSystems EBC-LP, Руководство по эксплуатации

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2.10.1 RS- 422 Mode Con figu ra tion
RS- 422 lev els are sup ported on both COM1 and COM2 with the in stal la tion of the op tional “Chip
Kit”, WinSystems part number CK- 75176-2. This kit pro vides the driver ICs nec es sary for a sin gle
chan nel of RS- 422. If two chan nels of RS- 422 are re quired then two kits will be needed. RS- 422 is a
4- wire point-to-point full- duplex in ter face al low ing much longer ca ble runs than are pos si ble with RS-
232. The dif fer en tial trans mit ter and re ceiver twisted pairs of fer a high de gree of noise im mu nity. RS-
422 usu ally re quires the lines be ter mi nated at both ends. This ter mi na tion can be ac com plished ei ther
on the ca ble or by in stall ing re sist ers on the board in lo ca tions re served for them. The method for
de ter min ing the cor rect re sis tor val ues is be yond the scope of this docu ment but it is rec om mended that
trial val ues of 100 ohms be used in all three lo ca tions at the re ceiver end. The fol low ing il lus tra tion
shows the cor rect mode jump er ing, driver IC in stal la tion, I/O con nec tor pin defi ni tions, and
ter mi na tion re sis tor lo ca tions for each of the chan nels when used in RS- 422 mode.
COM1 - RS- 422
* Important Note: All serial termination
components are surface mount 0805 packages. These should only be installed by surface mount
qualified individuals.
Page 2-8 EBC-LP OPERATIONS MANUAL 030530
WinSystems - "The Embedded Authority"
3 2 1
o o o
1 2 3
o o o
U24 - Not In stalled
U25 - In stalled
U26 - In stalled
1 o o 6
2 o o 7
3 o o 8
4 o o 9
5 o
J11 J12
COM1 DB9
N/C
TX+
TX-
N/C
GND
RX+
RX-
N/C
N/C
VCC
R17
R14
R11
RX+
RX-
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).