Kontron CP346 - Manual (Page 52)

Configuration CP346
Page 4 - 4 © 2005 Kontron Modular Computers GmbH ID 27253, Rev. 03
P R E L I M I N A R Y
4.1.2 RS422/485 Termination Jumpers
The CP346 offers onboard two 120 ohm termination resistors per channel, which can be used
to terminate the differential line pairs in case the serial channel is a beginning or end node of a
RS422/485 network.
4.1.3 Handshake Control in Half Duplex RS485 Mode
In the two-wire half-duplex RS485 mode a handshake mechanism is necessary to prevent the
sending and receiving of data at the same time over the same RS485 cabling. Otherwise a data
crash would occur.
For the handshake mechanism the driver enable (DE) and receiver enable (RE) signals of the
RS422/485 transceivers must be managed. This is achieved with the help of the CPLD logic
receiving the RTS or DTR serial signals as inputs and generating the DE and RE signals as
outputs for the transceivers. The Oxford OX16PCI954 driver uses the DTR signal for such con-
trol, but there may be other software on the market, where the RTS signal executes this task.
Therefore on the CP346 and CP346-OPT the input signal to the CPLD is configurable as
shown in the following tables:
Table 4-3: Termination Jumper Settings for CP346 and CP346-OPT
Ch.0 Ch.1 Ch.2 Ch.3 Setting Description
J7 J6 J3 J2
Open (default) Termination between TRXD± in half duplex mode or TXD± in full
duplex mode
Open: No 120 ohm termination
Set: 120 ohm term. between differential lines
Set
J8 J5 J4 J1
Open (default) Termination between RXD± in full duplex mode
Open: No 120 ohm termination
Set: 120 ohm term. between differential lines
Set
Table 4-4: RS485 Transceiver Control for CP346
Channel0 Channel1 Channel2 Channel3
R67 R68 R69 R70 R65 R66 R63 R64
DTR signal controls
DE/RE (default)
Open Set Open Set Open Set Open Set
RTS signal controls DE/RE Set Open Set Open Set Open Set Open
Table 4-5: RS485 Transceiver Control for CP346-OPT
Channel0 Channel1 Channel2 Channel3
R4 R3 R52 R48 R47 R26 R22 R20
DTR signal controls
DE/RE (default)
Open Set Open Set Open Set Open Set
RTS signal controls DE/RE Set Open Set Open Set Open Set Open