UM0842 datasheet(13/50 Pages) STMICROELECTRONICS

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UM0842

Configuration

Doc ID 16542 Rev 4

13/50

5.4

RS-232 and RS-485 transceivers

There are three RS-232 DB9 plug connectors and one RS-485 DB9 socket connector with a

Profibus DP compliant pinout available on the board.

UART0 features the full modem control signals and fully utilizes U10, U12 and partly U14

RS-232 transceivers. The RS232_0 signals are available through the CN13 connector.

Optionally when the U10 RS-232 transceiver is not soldered on the board, it is possible to

line in RS232_TXD and RS232_RXD signals from the CPU board to the CN13 connector.

UART1 features only RX/TX functionality and is connected to the U14 RS-232 transceiver

which RS232_1 signals are then available from the CN15 connector.

UART2 features only RX/TX functionality and uses U13 RS232 transceiver which RS232_2

signals are available from the CN14 connector. Optionally by setting jumpers JP12 and

JP13, the UART2 RX/TX lines can be connected to the RS-485 transceiver U11 whose

outputs are then available from connectors CN11 and CN12. The RS-485 transceiver U11

can be controlled through GPIO pins PL_GPIO77 (receiver enable, R70 - pull up) and

PL_GPIO78 (driver output enable, R73 pull down). Check the ST3485 datasheet for further

details about all possible transceiver configurations.

Table 5.

CAN1 transceiver settings

Jumper

Description

Configuration

JP4

CAN1 transceiver works in standby mode when JP4 is set.

CAN1 transceiver works in high-speed mode when JP4 is set

(Default).

CAN1 transceiver works in slope control mode when JP4 is

open.

JP5

CAN1 terminal 120Ω resistor is enabled when JP5 is loaded.

Default setting: loaded

12 3

Table 6.

UART2 RS-232/RS-485 configuration

Jumper

Description

Configuration

JP11

Connects +5.0 V to the RS-485 (R71, R72 and R74)

termination network.

Connects +3.3 V to the RS-485 (R71, R72 and R74)

termination network (Default).

12 3

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