Functional Description
CPB902
C P B 9 0 2 U s e r M a n u a l
54
© 2 0 0 8 F a s t w e l v . 1 . 5 b E
Figure 4.20:
Point-to-Point Connection of Two Modules in RS-422 Mode
Y
Z
A
B
RX+
RX-
TX+
TX-
on
120
DI
DE
RO
H/F
RS422/RS485
Converter
off
120
1
2
3
4
5
6
7
8
9
10
IDC10 Connector
(J5/J7/J9/J11)
1
2
3
4
5
6
7
8
9
10
Y
Z
A
B
on
120
DI
DE
RO
H/F
off
120
DCD
DSR
RXD
RTS
TXD
CTS
DTR
RI
GND
+5V
DCD
DSR
RXD
RTS
TXD
CTS
DTR
RI
GND
+5V
RS422/RS485
Converter
RX+
RX-
TX+
TX-
Figure 4.21:
Connection of Several Devices in RS-485 Mode
Y
Z
A
B
D+
D-
off
120
DI
DE
RO
H/F
on
120
1
2
3
4
5
6
7
8
9
10
Y
Z
A
B
D+
D-
off
120
DI
DE
RO
H/F
on
120
1
2
3
4
5
6
7
8
9
10
Terminating
Module
D+
D-
RO
DI
DE
RO
DI
DE
DCD
DSR
RXD
RTS
TXD
CTS
DTR
RI
GND
+5V
DCD
DSR
RXD
RTS
TXD
CTS
DTR
RI
GND
+5V
IDC10 Connector
(J5/J7/J9/J11)
IDC10 Connector
(J5/J7/J9/J11)
Terminating
Module
RS422/RS485
Converter
RS422/RS485
Converter
Peripheral
Module
Peripheral
Module
RS485 Converter
RS485 Converter
Figure 4.22 presents a diagram explaining functioning and mode selection for one of
COM3 – COM6 ports.
TXD_COM and RXD_COM are TTL level signals and are routed to UART16550 compatible serial
interface controller. RS-232 converter is activated on setting EN_COM=”1” and RS-422/RS-485
converter is activated when EN_COM=”0”. RXD_COM signal is multiplexed from the appropriate
converter. In RS-485 mode the TXEN_485 signal determines the data transfer direction, it switches
the channel between "receive" and "transmit" modes. This signal status can only be read. When
EN_COM=”0”, HF_485 allows to select RS-485 or RS-422 mode: HF_485=”1” corresponds to
RS-485 mode, HF_485=”0” – to RS-422.
