Hardware design questions - E1.20 RDM (Remote Device Management) Protocol Forums

ELMVideo · July 7th, 2012

Thank you Eric J. for the responses.

As for question 1 above, I'm asking in a general sense. The E1.20 document shows a reference circuit with Rt2 (120 ohm) and the biasing network, I just want to make sure I'm understanding where the two belong. The biasing network should be (for a 1 in 2+ out circuit) on the 2+ outputs (simulating controllers) and the (switchable) termination on the one input of this type of circuit?

Per question 2, I've designed the circuit with a microprocessor to handle the "Transmit Enable" and "Receive Enable" data direction etc., as for the 485 IC's (75176) the 'R' data out of theses IC's need to combine to 'simulate' a collision. Just to verify,

Quote: Once you have that, you can use either a passive combining network, or an AND gate for the data signals.

so each "R" output (Receive data of a 75176 IC) tieing to a 100 ohm resistor and then the resistors connected together and tied to the "D" input of the 'main' 75176 IC would suffice?

Thanks for the note on the timing, I'll make note of it.

Thanks again,
Eric M

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July 7th, 2012	#3
ELMVideo Junior Member Join Date: Jul 2012 Posts: 4	Thank you Eric J. for the responses. As for question 1 above, I'm asking in a general sense. The E1.20 document shows a reference circuit with Rt2 (120 ohm) and the biasing network, I just want to make sure I'm understanding where the two belong. The biasing network should be (for a 1 in 2+ out circuit) on the 2+ outputs (simulating controllers) and the (switchable) termination on the one input of this type of circuit? Per question 2, I've designed the circuit with a microprocessor to handle the "Transmit Enable" and "Receive Enable" data direction etc., as for the 485 IC's (75176) the 'R' data out of theses IC's need to combine to 'simulate' a collision. Just to verify, Quote: Once you have that, you can use either a passive combining network, or an AND gate for the data signals. so each "R" output (Receive data of a 75176 IC) tieing to a 100 ohm resistor and then the resistors connected together and tied to the "D" input of the 'main' 75176 IC would suffice? Thanks for the note on the timing, I'll make note of it. Thanks again, Eric M