kieran@adds.newyork.NCR.COM (Joe Cabana) (04/08/88)
In article <494@flatline.UUCP> phaedrus@flatline.UUCP (james hartman) writes: >In article <2617@tekgen.TEK.COM>, jonh@tekgen.TEK.COM (Jon Howell) writes: > >[Description of data going out to one pak going to both on his L2 system] > >As with the 300bps modem pack drivers (/m1 and /m2), /t2 and /t3 cannot be >used at the same time. Why? They both use the ACIApak driver under L2, so >any data that goes out to either one is run through that driver. The only >difference between /t2 and /t3 is which slot of the MPI the RS-232 is in >(since 1 and 4 have the hardware support for interrupts and slots 2 and 3 >do not). This, unfortunately, is a silly oversight on the part of the Shack >and/or Microware. [This information is taken from the old L1 update package >that was put out before the CC3 for various compatibility reasons.] > Actually the reason characters appear on both ports is because of a hardware limitation in the RS-232 packs themselves, not a software problem. If you look at the schematics in the RS-232 pack tech. ref. manual you'll find the RS-232 packs are setup to use the slot select lines to enable thier ROMS but NOT the UARTS. This means that no matter what slot you put the pack in, the UART will always be at the same address. There is no way to put two RS-232 packs in at once without hardware mods to change the address of one pack and software changes to use the new address. The reason for two drivers (as far as I can tell) is to allow you a choice of slots in case of conflict. (OS-9 still needs to know which slot has the ROM). J. E. Cabana kieran@adds.newyork.NCR.COM
pete@wlbr.EATON.COM (Pete Lyall) (04/09/88)
In article <564@adds.newyork.NCR.COM> kieran@adds.newyork.NCR.COM (Joe Cabana) writes: >In article <494@flatline.UUCP> phaedrus@flatline.UUCP (james hartman) writes: >>In article <2617@tekgen.TEK.COM>, jonh@tekgen.TEK.COM (Jon Howell) writes: >> >>[Description of data going out to one pak going to both on his L2 system] >> > >Actually the reason characters appear on both ports is because of a hardware >limitation in the RS-232 packs themselves, not a software problem. >If you look at the schematics in the RS-232 pack tech. ref. manual you'll find >the RS-232 packs are setup to use the slot select lines to enable thier ROMS >but NOT the UARTS. >[text deleted]..................................The reason for two >drivers (as far as I can tell) is to allow you a choice of slots in >case of conflict. (OS-9 still needs to know which slot has the ROM). > Actually, the ROM is never mapped in at all. It contains an exceptionally primitive terminal program that was in the same address space ($C000-$DFFF) as the Coco's disk controller rom. The roms are mapped out under any 64k RAM scenario anyway, an are consequentially invisible to OS9 as well. The only purpose for juggling slot select was to be able to allow passage of the 6551's interrupt - in this case passed as a CART interrupt (FIRQ) - through the multipak multiplexor and into the coco where it could be software mangled (stack frame diddling) into looking like an IRQ. On the coco3 they simply program the GIME to make the arriving CART post an IRQ. In the latter case though, the method of IRQ handling is improper and characters are frequently dropped (even at lower baud rates). This has led to several folks physically connecting the 6551's IRQ line to the 6809's IRQ line. I can provide installation details if interest merits. -- Pete Lyall (OS9 Users Group VP)| DELPHI: OS9UGVP | Eaton Corp.(818)-706-5693 Compuserve: 76703,4230 (OS9 Sysop) OS9 (home): (805)-985-0632 (24hr./1200 baud) Internet: pete@wlbr.eaton.com UUCP: {ihnp4,scgvax,jplgodo,voder}!wlbr!pete