You should contact an expert on this subject. One such expert is Link Technology......Email me and I can get you a name and telephone number. In order to have successful IDSN connection you will need an ISDN interface coupling circuit, an ISDN interface transceiver, and an HDLC controller of some sort. Dialing is controlled through a process that is not too hard but takes a sizeable batch of software. In the past ISDN intefaces I have seen have been implemented on processors such as MC68308 or MC68332.

I suspect that a higher performance 8051 derivative part such as a Cygnal C8051F126 running at 25 or 30 MHz could handle the code to implement an ISDN interface as long as you did an outboard USDN transceiver such as the Motorola MC145574 and a hardware HDLC controller that could accept a TDM bus. A Motorla part that can do this HDLC job is the DDLC chip (MC145488) which may no longer be available.

Michael Karas