U009@CCIW.BITNET (11/16/89)
Received: from CCIW.BITNET by McMaster.CA; Thu, 16 Nov 89 09:21 EDT Date: Thu 16 11 89 07:44:00 EST From: U009@CCIW.BITNET Subject: Blitz- my impressions To: Info-Atari16@Score.Stanford.edu ( Hi again. Just a couple of thoughts about the Blitz duplicator. Great innovation. Ranks up there with the Magic Sac and Spectre as a great hack. All the more impressive because it's the type of thing: "Gee, I could have thought of that!" In fact, after the first disk came off, that's exactly what I thought. How does it work? It seems to control the "from" drive by the normal floppy ports, using pulse width modulation (PWM) on the MOTOR ON line to adjust the floppy rotation speed. It controls the "to" floppy completely thru the parallel printer port, and I imagine it uses PWM there too. The program observes the index pulses from both drives and adjusts the rates so both floppies rotate in synchronism. The read data from the "from" drive is connected directly to the write data line on the "to" drive (see table below). When both drives are synchronized, the write gate line is activated for 1 revolution and all the data is copied to the "to" drive, keeping all pulse widths and relative timings identical. The routine then advances to the next track and repeats the operation. The same process could be used to build a stand-alone duplicator for 5-1/4" drives too. Probably an 8031 or even an 8748 would be all that is required in a processor. A couple of switches to select 40 or 80 tracks, 1 or 2 sides (or default to 2, it's only an extra 20 seconds) and the 2 drives. From the previous posting (with signal names added): > COMPUTER (INTERNAL) COMPUTER > OR DRIVE 1 (EXTERNAL) DRIVE 2 PRINTER > OUT PORT IN PORT OUT PORT > ------------------------------------------------------------------------- > 14 PIN DIN PLUG (MALE) 14 PIN DIN PLUG (MALE) 25 PIN DB PLUG (MALE) > ------------------------------------------------------------------------- > 1 - Read Data > 2 --WHITE--------------- 2 - Side 0 Select > Logic Gnd 3 --VIOLET--VIOLET-- 3 - Logic Ground > 4 --BLACK--------------- 9 - Index Pulse > 5 --BLUE---------------- 3 - Drive 0 Select > 6 --PEACH/BLACK--------- 3 - Drive 1 Select > 7 --GREEN-------------- 20 - Logic Ground > 8 --BLUE/BLACK---------- 7 - Motor ON > 9 --YELLOW-------------- 6 - Direction IN > 10 --WHITE/BLACK--------- 5 - Step Pulse > Read Data 1 --GRAY--PEACH-- 11 - Write Data > 12 --BROWN--------------- 4 - Write Gate > 13 --ORANGE------------- 11 - Track 0 > 14 --RED----------------- 8 - Write Protect > SHIELD --------------- SHIELD ----------------- SHIELD Regards, Stu Beal, VE3MWM, (U009@CCIW.BITNET), National Water Research Institute, Burlington, Ontario, Canada.