Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!ucbvax!DOCKMASTER.ARPA!McAllister
From: McAllister@DOCKMASTER.ARPA
Newsgroups: comp.sys.apple
Subject: TIC and ProDOS
Message-ID: <880801114205.280649@DOCKMASTER.ARPA>
Date: 1 Aug 88 11:42:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 23

On 06/26/88, Subject: tic's interrupt handlers, Don Elton wrote:

>TIC (Talk is Cheap) uses the standard ProDOS interrupt vectors and a 256 byte
interrupt buffer for irq handling.<

In trying to discover why TIC doesn't work with my IIc System Clock, I see
that the system global page is modified:

from    $BF00 JMP BFB7             to    $BF00 JMP $BF4B

                                         $BF4B PHP
                                               SEI
                                               JMP $BFB7

This has the effect of turning off interrupts on *all* ProDOS MLI calls. Since
clocks are read by an MLI call, GET_TIME, and the IIc System Clock driver
takes an inordinate amount of time, serial port interrupts are lost.  This is
only one of the reasons why received data is garbled.

Why do you disable interrupts Don Elton?  Why do you modify the use of the
system global page?

                         McAllister at Dockmaster.ARPA