ls1020a duart can support RS485 half duplex

[haixiang_liu]

Just want to confirm whether ls1020a duart can support RS485 half duplex. Don't see it in the ls1020a reference manual.

[alexander_yakov · Accepted solution]

RS485 is electrical standard, from the LS1020A hardware point of view UART should be used to implement RS485.

RS485 half duplex means transmission and reception is performed over the same line (twisted pair). So, you have to manage RS485 line driver and explicitly switch it from reception to transmission. This is usually done in software, by using any GPIO pin. Also, in some types of UART, there is a support for "hardware flow control", so the transmitter can automatically assert hardware flow control line "request to send" (RTS) to start the transmission. There are two types of UART in LS1020A processor - DUART and LPUART. DUART does not support hardware flow control and requires GPIO to manage transmission direction. LPUART supports hardware flow control, so RTS may be used to control transmission direction.

Have a great day,
Alexander,
TIC

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[haixiang_liu]

And whether lpuart can support 460800 baud rate?

[alexander_yakov]

No, we do not offer application note for LPUART in RS485 application.

Maximum baudrate is specified in device datasheet as fPLAT/(2 x 4) where fPLAT is platform clock.

However, it is said that "The actual attainable baud rate is limited by the latency of interrupt processing".

So, this means the maximum baudrate is limited by software.

[haixiang_liu]

thanks for your answer, alexander

[haixiang_liu]

And one more question, do you have any application note how to use lpuart to driver rs485?

[haixiang_liu]

thanks very much for your reply and it answer my question. thanks.