Paul R. Grupp <GRUPP@Mit-Mc.ARPA> (11/19/84)
WHAT? MOST uarts alow for the generation of a BREAK condition to be sent out the rs-232 line. Given this most (all that I've seen) modems when they see this condition it turn send it out the phone line... The "problem" seems to be that few BIOSes alow for a BREAK sent from the TTY to be sent to the application program. For that matter the BDOS calls to get TTY input can't even pass along a NULL (NULL=0h and that is returned from the direct consol i/o call if NO character is ready)! But with some software mods you CAN make your modem send a break. One way to do this is to have the application program do it's own i/o and pass along a break to the uart. Another is to define some sequence of characters that when seen will in turn signal the uart to send a break rather than sending the string i.e. ^_B (ctrl-underscore then "B") sends break, and to send a ^_ you would type it twice. -Paul