RS485 NXP Implementation

[abderrezak]

Hi every body, 

I wish you a happy new year :smileyhappy:

I develop a command bord around the LPC1788 on which I have used many peripherals com. On of theme is UART.

On this UART user will use an RS485 implementation (Of course I added a RS485 transceivers). Regarding to the software, I wish to use the NXP Implementation of the RS485 (RS485CTRL, RS485DLY, RS485ADRMATCH).

After reading the related section on the UM, I am confused on how to use the RS485 filtering address. And it seems little bit hard to find a Serial Terminal to test the communication because of: the setting to '1' of the parity bit of address (set to '0' for data)

In addition if I have to use a parity checking at receive and send (odd or even) how the NXP-RS485 will differentiate the address from data?

In my application, it will be useful to associate the first byte to address and the rest is always data. Can I use this kind of checking address mechanism (Of course with no software checking)

Thank you

[Carlos_Mendoza]

Hi Abderrezak,

Happy new year to you too!

I would recommend you to take a look to the section17.5.22 for more information about the distinction between address and data in received data in the RS-485 mode of operation:

http://www.nxp.com/documents/user_manual/UM10470.pdf 

About your last question, it is not possible to perform the address checking mechanism you mention automatically, it will have to be implemented by software so I would recommend you to use the Auto Address Detection (AAD) mode instead.

Hope it helps!

Best Regards,
Carlos Mendoza
Technical Support Engineer