control characters with bit 8 high & ppp

["Richard E. Hawkins Esq." <hawk@eyry.econ.iastate.edu>]

I've finally managed to make a ppp connection over my isn (not isdn)
line; the connection is made and i can ping other machines.

I've set asyncmap at both ends to 0xFFFFFFFF to block all control
characters from being used.  However, the hardware on the isn line
uses ^S/^Q.  However, it does this in hyardware for both the values
themselves, and for the corresponding values with bit 8 high.  So 
my connection doesn't stay up long enough to do anything useful--
even launching & xterm & telnet session is too much for it.

So is there any way to add the "high" control characters to the 
asyncmap?  Or do I have to switch over to a 6 bit slip instead
of ppp?

rick