Atari SX212 modem ports

[eccofonic]

Anyone know if it's possible to use the Atari SX212 modem as a "bridge" connection (like a null modem) between an Atari ST (or IBM PC) and an Atari 8-bit using the SIO port and 25-pin serial port on the back of the SX212?

 

Or is this impossible?

[+rdemming]

Anyone know if it's possible to use the Atari SX212 modem as a "bridge" connection (like a null modem) between an Atari ST (or IBM PC) and an Atari 8-bit using the SIO port and 25-pin serial port on the back of the SX212?

 

Or is this impossible?

 

I don't know anything about the Atari modem, but generally a modem is made to connect to a telephone network. Directly connecting two modems together probably does not work since you are then missing the voltage that is normally put on the line by the telephone exchange.

 

But why not use one of the various SIO2PC devices to connect the Atari 8-bit to PC (APE/AspeQt) or Atari ST (800XL DJ)? That is much more user-friendly than transporting data via a terminal program.

 

Robert

Edited June 10, 2011 by rdemming

[Fox-1 / mnx]

I don't know anything about the Atari modem, but generally a modem is made to connect to a telephone network.

I think this modem is the one with dual interface (SIO for 8-bit / RS232 for ST). If I understand it right I think he wants to connect the modem to an XL/XE while using the RS232 on the modem to communicate with external devices (neglecting the modem itself).

 

This MAY be possible (maybe with some custom wiring). The modem is just a standard RS232 one with internal R-Verter or SIO2PC-like device. If you can interact between the 2 physical connectors on the modem depends on how the SIO circuit is wired in the modem itself. Can't answer that as I just don't know.

[+rdemming]

Ah, I see. It is a modem with dual connectors. Out of the box it won't work because, if SIO and RS232 are parallel, both SIO and RS232 would be logically wired to each other in a "straight" manner instead of "crossed". In other words SIO and RS232 serial in are connected and serial out are connected. So it least needs a modification that swaps the serial in and out lines on the SIO side or the RS232 side so SIO in is "logically" (not directly physically) connected to RS232 out and SIO out is connected to RS232 in.

Also command line of SIO must map to DSR, CTS or RI on RS232 side.

 

So you need to open the modem and see how the SIO and RS232 lines are connected inside the modem. If they are connected to a MAX232 chip it might be possible to modify.

 

Robert

Edited June 10, 2011 by rdemming

[kurtm]

Ah, I see. It is a modem with dual connectors. Out of the box it won't work because, if SIO and RS232 are parallel, both SIO and RS232 would be logically wired to each other in a "straight" manner instead of "crossed". In other words SIO and RS232 serial in are connected and serial out are connected. So it least needs a modification that swaps the serial in and out lines on the SIO side or the RS232 side so SIO in is "logically" (not directly physically) connected to RS232 out and SIO out is connected to RS232 in.

Also command line of SIO must map to DSR, CTS or RI on RS232 side.

 

So you need to open the modem and see how the SIO and RS232 lines are connected inside the modem. If they are connected to a MAX232 chip it might be possible to modify.

 

Robert

 

If that's true, you can just make an adapter for outside the case. Redirect the lines where they need to go. It'd be worth trying just a null modem adapter first to see if that would work. The big trick would be that you wouldn't want the modem "butting in" on the conversation.

 

--Kurt

[sloopy]

the way the modem is internally designed, both the rs-232 and the SIO port come in, and go straight to the serial chip... the RS232 lines go through a 1488/1489 line level converts first... so it would be simple to mod the modem to work as a SIO2PC device, probly all that would be needed is to disconnect the modem serial, cross tx/rx and add the wiring for the command line...

 

this is my SX-212, i modified it with a SIO2PC-usb and a SDrive internally...

http://sloopy.digitalglass.us/theSIOConnection/

 

sloopy.

[+rdemming]

The big trick would be that you wouldn't want the modem "butting in" on the conversation.

 

The chances are high the modem will react. Thus indeed you probably need to cut the serial in/out wires to the modem chip.

 

Robert

Edited June 10, 2011 by rdemming