UM0843 datasheet(16/48 Pages) STMICROELECTRONICS

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Block descriptions

UM0843

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Doc ID16543 Rev 2

UART2 features only RX/TX functionality. It uses the RS232 transceiver at U32 and its

RS232_2 signals are available on the P4 connector.

UART3 features only RX/TX functionality. It uses the RS232 transceiver at U33 and its

RS232_2 signals are available on the P5 connector.

UART4 features only RX/TX functionality. It uses the RS232 transceiver at U33 and its

RS232_2 signals are available on the P6 connector.

UART5 features only RX/TX functionality. It uses the RS232 transceiver at U34 and its

RS232_2 signals are available on the P7 connector.

Do not install jumpers in J31 when UART3, UART4 and UART5 are enabled and used.

6.5

HDLC-RS485

There are two HDLC-RS485s on the board, they are connected to RS485 transceiver (U16

and U60) and use DB9 connectors (P1 and P8).

HDLC-RS485 features the half-duplex communication, RXD and TXD single-end signals are

connected to one RS485 transceiver, by enabling CTS function, it can detect and avoid all

the possible bus conflict.

For the correct functionality of the HDLC-RS485, it is necessary to clock them by external

clock (TCLK, RCLK), the maxim clock frequency is 3.88MHz, There are two ways to deliver

the clocks to CPU. The default option is to use on-board clocks (819.2KHz) that are

generated by U38 CPLD.

By default the on-board clock configuration of HDLC-RS485-1 is selected as shown in

Table 9.

By default the on-board clock configuration of HDLC-RS485-2 is selected as shown in

Table 10.

Table 9.

HDLC-RS485-1 on-board clock jumpers

Jumper

Description

Configuration

JP65

Supply on-board clocks or

external clocks to CPU for

HDLC-RS485-1 TCLK.

(Default - fitted) to use on board

clocks (PIN-1)

JP66

Supply on-board clocks or

external clocks to CPU for

HDLC-RS485-1 RCLK. (Default

- fitted) to use on board clocks

(PIN-1)

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