rs422 5v level doubt

[raman00084]

in my ac servo drive it is written +step, -step rs422 5v level. my doubt is that can i convert the pic microcontroller i/o pulses to rs422 using line driver am26ls31 and connect to the step+ and step- pins. should i must use ant resistor in series kindly help

regards
kalyann

 

[KlausST]

Hi,

Rs422 is differential sgnalling. You need two signal wires to transmit.
.. and best is to use a dedicated rs422 receiver. Am26ls32? Usually this is built in the servo.

Series resistors...
Look into the transmitter datasheet, some have built in, some don' t.
In the datasheet you may find informations on how to set up a proper transmission line.
Also on how to use termination resistors.

Klaus

 

[barry]

1) RS-422 has a minimum level of +/- 2V, maximum of +/-6V. 5 Volts doesn't enter into it.
2) The 26LS31 is specifically designed as an RS-422 driver. The only resistor you need is a parallel termination at the receiver(servo drive); you don't need any series resistors.

 

[raman00084]

what is the voltage level of rs422

what is the voltage level of rs422, is rs422 operates only in 5v. 12v and 24v rs422 available?

 

[ARQuattr]

Re: what is the voltage level of rs422

I'm not sure the voltage level is defined in the standard, although typically it is run at 5V. It really depends on the transceivers used. I used some H-bridge drivers after the RS-485 transmitter to run a RS-485-like bus at 24V.

 

[KlausST]

Hi,

what is the voltage level of rs422, is rs422 operates only in 5v. 12v and 24v rs422 available?

The signal levels are defined in standard.
...Because for a safe data transmission the voltages are important.

*****

Supply voltage of the devices is not important for safe data transmission, therefore it is likely that this is not defined in standards.

*****

There must be a big market for the manufacturers if they decide to produce RS422 transmittiers with higher supply voltage.
It is an extra effort to design a voltage regaulator with its power disspation in a chip.

I personally can´t hink of many applications that use RS422 without other 5V or 3.3V supplied ICs like ucontroller, modbus or profibus interface chips.
So 5V or 3.3V should be available on the PCB.

Klaus