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analog mux for RS232 RS485

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treitmey

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rs232 mux

Has anyone used something like a mpc508 to mux a signal to different devices?
https://focus.ti.com/lit/ds/symlink/mpc508.pdf

I'd like to use the same 4 wire RJ for either
pwr,gnd,RS232 TX, RS232 RX.
or
pwr,gnd,RS485 A, RS485 B

So I wanted to know if some kind of mux exits for a RS232 level?
ps my board is 5V.
Currently I will just use some jumper to route the signal to either MAX232 or MAX485 chip.
 

FvM

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mux rs232

I'm not aware of dedicated MUX devices for RS232 or RS485 interface. Of course you can use any existing MUX device according to your specification.

I guess, that't it less expensive and more realiable anyway to use individual driver devices for each interface and perform the mux action at a logic level. If you intend a multi purpose RS232/RS485 interface, there are suitable devices available, but much more expensive than separate industry standard drivers.
 

treitmey

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analog mux chip

I'm not sure what you mean by this
Of course you can use any existing MUX device according to your
specification.

Perhaps I wasn't clear.
I want to use the same RJ11 two wires for either RS232 or RS485.
But is there a chip that would route those types of levels(rs232) to the
MAX232 chip or to the MAX485 chip without losses that would make rs232/rs485 fail?

Perhaps a wire jumper is best after all.
 

FvM

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max232 with mux

without losses that would make rs232/rs485 fail?
This actually depends on your specification. A MUX with kohm series resistance, as you suggested, can work only under very limited conditions (speed, cable capacitance, termination), but it possibly can. Another point is the required RS232 level, not said in your post. But depending on your requirementa, some existing analog switches/multiplexers/discrete transistor switches can do, also with considerably lower "losses". The costs and required board space may be inadequate for your application.

Did you check the MAX3160 family of multiprotocol transceivers?
 

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mux rs485

Yes I looked at multi-protocol chips, and that may help,...
but to take it a step further, I would add a 3rd destination
a custom current loop detector.

Jumper wires are still able to work.
My option for a chip(mux) I think is held up because of
the true levels of RS232. +25 to -25 for the receiver.
Clipping I think would work OK, but if the chip see's this as
ie:ESD and shorts it to ground, that wouldn't work.
 

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