rs485 4 wire (full duplex)

[RavensFan]

Just so you know,  in English "doubt" means something that you don't believe.  "I doubt that you've hiked to the North Pole".  "Question" means ask about something you don't know and want to find out about.  "I have a question, have you ever hiked to the North Pole?"  "Doubt" implies a negative connotation to something, "I don't believe".  "Question" is basically neutral, "I don't know".

So, have your questions been answered, or are there any other questions still on your mind?

[srm@viewpointusa.com]

your original post is refering to a differntial encoder output from your encoder simulator that you are trying to bring into fpga ttl inputs.  often differential drivers are implemented with 422 or 485 driver chips.  485 has higher driver level and slew rates allowing for faster and farther transmission than 422.

depending on the drive level (if 5V) from the encoder simulator, you may be able to directly connect encoder A and B to fpga input giving up noise immunity. if you want to do it right, you would need a differential encoder to ttl conditioner.  you could use 2 of the 485 half duplex converters (one for each A and B)

[FrankyCam]

Thank you very much for English lesson!

Coming back my original post...I have

1) an  SSI absolute encoder with RS422 output. By a TTL/RS422 converter i obtain TTL signal. I wrote fpga C-rio program to send clock and to receive data from this encoder... and it works fine.

2) an encoder simulator SSI with RS485 4 wire. My QUESTION is about RS485 4 wire, because I own only TTL/RS485 2 wire converter. Your suggestion (@Stu) is to use a RS485 half duplex converter to send clock and another RS485 converter to receive data, isnt'it?

[srm@viewpointusa.com]

yes, that is my suggestion.  the two wire device is meant for half duplex communication where the direction is determined by the rts line.  you need send and recieve simultaneously.

[FrankyCam]

Tank you Stu. I'll try it and post results.