RS232 to synch modem

[Graziano]

Hi People!
   I have a cFP-2020.  It runs an embedded app.  I need to communicate through cFP2020 RS232 port to a synchronous modem, i.e. I can't send data with start bit, stop bit, etc...

   Does anyone know about some device which can accept a buffer from RS232, convert it to HDLC protocol, and send data in synchronous fashon to a modem? I think I can't make the FP-2020 RS232 port work as a synchronous serial port..... (am I wrong?).

    I'm really stuck here.... help really appreciated!

   graziano

[Castel]

Hi Graziano,

I can share with you this link that talks about Synchronous or Asynchronous serial communcation:

http://digital.ni.com/public.nsf/websearch/ECCAC3C8B9A2A31186256F0B005EEEF7?OpenDocument

But, as the document explains, the term synchronous is NOT to be confused with its use when defining whether a given hardware connection shares a common clock or timebase, rather these terms refer to how the VISA functions behave with respect to their calling threads.

In order to confirm your doubt, I think you have to read also:

http://digital.ni.com/public.nsf/websearch/CBADAC4F0EC854578525644F004CB71A?OpenDocument

Regards

MarcoC

[Graziano]

Hi MarcoC, thanks.

   The second link is useful, it tells me I'm unable to drive a Synchronous modem through PC RS232 port.  It already seemed to me...... because of the UART.

   Maybe I'm going to develop an embedded device which converts my asynchronous serial protocol to a Synchronous bit stream.  This device should recognise a valid HDLC packet, and when it's buffered, it should trasmit each bit synchronously to a modem.  Of course, this is possible with a Microcontroller (I was thinking on using Freescale HC08....).  But.... how to send data to my synchronous modem?? Is it enough to send bit at the Tx line???? I'm completely new to this issue, so..... if anybody has any idea....

   (I've already searched for commercial embedded devices which do this, but..... my application is not common, and I can't be shure MY hdlc protocol will fit with commercial HW....)

  Thanks!

graziano