From: Marko Mäkelä (marko.makela_at_hut.fi)
Date: 2004-04-19 10:23:22
On Mon, Apr 19, 2004 at 12:45:47AM -0700, Larry Mollica wrote: > One interesting tidbit, the OPEN statement allows 4-31 as IEEE488 > addresses, with 0-3 used for PET internal devices. But we found (ok, > by accident), that you can address IEEE488 addresses below 4 by using > values over 31, like > OPEN 1,34 > to talk to IEEE488 bus address 3. Wouldn't that access device 2 (32+2=34)? On the Commodore serial bus, the device number is simply ORed with the bus command. I doubt that the TALK command (e.g., GET# or INPUT# from the file) would work with a device number in the 32..62 range. On the Commodore 64, typing LOAD"FILE",88 locks up the computer. (That's device number $58 hexadecimal.) BTW, there is some magic in the high-order bits of the file number, and possibly device number. One of them controls CR to CR/LF transformation, and setting another bit avoids sending the secondary address, if I remember correctly. This is on the Commodore serial bus; I haven't disassembled the PET firmware. Marko Message was sent through the cbm-hackers mailing list
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