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CPU-1474/84 User Manual
24 CPU-1474/84_UserMan_En_2.0
J17: Serial ports 1 and 2
J17 makes available the following serial ports:
•
Serial 1, RS232 only (called Serial A in the BIOS)
•
Serial 2, RS232 / RS422 / RS485, software selectable from BIOS (called Serial B in the BIOS)
Figure 2. J17 connector layout
Pin # Signal Function Pin # Signal Function
1 DCD1
Serial 1
2 DSR1
Serial 1
3 RX1 4 RTS1
5 TX1 6 CTS1
7 DTR1 8 RI1
9
GND Ground signal
10
DCD2
Serial 2
11 DSR2
Serial 2
12 RX2
13 RTS2 14 TX2
15 CTS2 16 DTR2
17 RI2 18 GND Ground signal
Table 10. J17 Connector pinout: RS232 mode
RS422 RS485
Pin # Signal Function In/out Signal Function In/out Pin #
10 -TX Transmit data Out -TX/-RX Transmit/Receive data In / Out 10
11
-- Not connected -- -- Not connected --
11
12 +TX Transmit Data Out +TX/+RX Transmit/Receive data In / Out 12
13 -- Not connected -- -- Not connected -- 13
14 -RX Receive Data In -- Not connected -- 14
15 -- Not connected -- -- Not connected -- 15
16 +RX Receive Data In -- Not connected -- 16
17 -- Not connected -- -- Not connected -- 17
18 Ground Signal ground -- Ground Signal ground -- 18
Table 11. J17 connector pinout - Serial Port 2 - RS422 / RS485 modes
NOTE:
If the serial port is used in RS485 mode, the bi-directional line must be controlled via software, using the
Data Terminal Ready (DTR) signal of the serial controller. This signal is defined by bit 0 of the UART Modem
Control Register (MCR) and the bi-directional line is controlled as follows:
•
- bit 0 of the MCR register = 0 means RS485 line receiving
•
- bit 0 of the MCR register = 1 means RS485 line transmitting
The I/O address of the MCR is "Serial port Base address"+4H