Specifications

COM3/COM4 - RS- 232
COM3 and COM4 are RS- 232 only and are ter mi nated at J4. An adapter ca ble is avail able from
WinSystems (P/N CBL-173-1), which adapts J4 to two stan dard DB9M con nec tors. The pin defi ni tions
for J4 are shown here :
2.9.1 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”, Win Sys tems 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 s i 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 p lished 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 t ra 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.
030923 OPERATIONS MANUAL EBC-BX Page 2 - 7
WinSystems - "The Embedded Systems Authority"
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COM3 DCD
COM3 RX
COM3 TX
COM3 DTR
GND
COM4 DCD
COM4 RX
COM4 TX
COM4 DTR
GND
COM3 DSR
COM3 RTS
COM3 CTS
COM3 RI
N/C
COM4 DSR
COM4 RTS
COM4 CTS
COM4 RI
N/C
J4