ford@crash.CTS.COM (Michael Ditto) (07/25/87)
In article <2146@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes: >in article <13964@watmath.UUCP>, sbmueller@watmath.UUCP (Stephan Mueller) says: >> What must I do to the animal to have it do automatic diskchanges? (I've had >> it longer than the warranty, so I ain't worried about breaking nuthin.) > >The diskchange signal is usually a function of the drive mechanism. [...] Also remember that Amiga disk drives are "standard" drives PLUS a small circuit, which in the case of drives capable of detecting media-removal, includes a LATCH of the media-change line, cleared by the STEP signal. The schematic for this circuit is in the A1000 Schematics package. -- Michael "Ford" Ditto -=] Ford [=- P.O. Box 1721 ford@crash.CTS.COM Bonita, CA 92002 ford%oz@prep.mit.ai.edu
wtm@neoucom.UUCP (Bill Mayhew) (07/27/87)
You can order the Amiga schematics from the C-A people in West Chester, PA. I can't find the price right now, but it is around $25. C-A accepts only check or money order. The address is Amiga Technical Support 1200 Wilson Dr. West Chester, PA 19380 The phone # I have on file is 215-431-9100, but I'm not sure that it is current. There is a PAL chip on the drive interface board. It does at least three things I know of. 1. The motor control lead is broken down into two signals: motor on and motor off. These basically toggle a flip-flop on and off to save the state of the motor 2. The dirve's media change lead sets a flip flop, so that if the O/S is busy doing something else when the user swaps disks, that the event is not lost. The motor step lead is used to clear the disk change output. 3. The PAL can be polled by pulsing some of the inputs (forget just which ones at the moment). The PAL puts out a 32 bit device ID code so that the O/S knows what sort of drive it is. This is done when DOS boots. That's why a 1050 5.25" drive must be switched on before booting, else DOS won't know it's there. Other than the above exceptions, my best recollection is that the rest of the drive signals are off-the-shelf. Note that the little 1040 (or whatever the # is) 3.5 inch drives block DC power to subsquent drives in the string. The purpose being to prevent some idiot from plugging in 18 drives and sending his/her Amiga's power supply into a core meltdown. You can add more than one external drive by supplying it 5 and 12 volts from one of those wall-dongle type power packs. A while back Radio Shark had some left over from the Coleco Adam or some other brain damaged marketing attempt; you may still be able to pick one up (power pack, that is). Hope this gives you a few ideas,... Bill (wtm@neoucom.UUCP)
daveh@cbmvax.UUCP (Dave Haynie) (07/29/87)
in article <641@neoucom.UUCP>, wtm@neoucom.UUCP (Bill Mayhew) says: > Summary: Drives have a PAL chip > > There is a PAL chip on the drive interface board. It does at least > three things I know of. Actually, it's usually an open-collector NAND gate and a D-type flip flop. The original external 3.5" drive uses a 74LS38 and a 74LS74 for this function; the 3.5" drive has the simplest ID code, which is produced on the RDY line by the flip flop. The 5.25" drive has an additional chip, the 74LS132, which is another 2 input x 4 device NAND, but with schmitt inputs. This drive, being self-powered, also has a voltage sensor that gates the Read/Write line to the floppy disk, so that if the host Amiga is turned off, no accidental writes will take place. All the functional descriptions listed look OK, and I guess they could even be implemented with a PAL, though it would cost much more than a pair of TTL parts. > Note that the little 1040 (or whatever the # is) 3.5 inch > drives block DC power to subsquent drives in the string. The > purpose being to prevent some idiot from plugging in 18 drives and > sending his/her Amiga's power supply into a core meltdown. The 1010 drives actually pass +5V, but not +12V. The +12V supply is used on most of the 3.5" and 5.25" drives as a motor supply. All of the logic on both drives can be drive only with +5V. That's why, if you hook up a second external 3.5" drive with no +12V supply, the Amiga OS will recoignze the drive, but list it as BAD. Also, the passing of +5V is important to self powered drives like the 1020 (5.25"). If the power isn't passed, the drive will think that the host Amiga system is shut off, and it will not let WRITE be gated through.n > Bill -- Dave Haynie Commodore-Amiga Usenet: {ihnp4|caip|rutgers}!cbmvax!daveh "The A2000 Guy" PLINK : D-DAVE H BIX : hazy "Catch a wave and you're sittin' on top of the world" -Beach Boys
grr@cbmvax.UUCP (George Robbins) (07/30/87)
In article <2165@cbmvax.UUCP> daveh@cbmvax.UUCP (Dave Haynie) writes: > in article <641@neoucom.UUCP>, wtm@neoucom.UUCP (Bill Mayhew) says: > > There is a PAL chip on the drive interface board. > > Actually, it's usually an open-collector NAND gate and a D-type flip > flop. The original external 3.5" drive uses a 74LS38 and a 74LS74 > for this function... Some of the drives do have a strangely marked Japanese branded DIP. It turns out that this part is, in fact, comparable to a 74LS38, a high-current, open collector TTL driver. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)
cmcmanis%pepper@Sun.COM (Chuck McManis) (07/30/87)
In article <641@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: > >You can order the Amiga schematics from the C-A people in West Chester, PA. >There is a PAL chip on the drive interface board. It does at least >three things I know of. Huh? In my schematics the 3.5" pcb has a 74LS74 and a 7438, whereas the 5.25" drive has these plus a 74LS132 and a PST518B (labeled as Q1) it acts as a schmidt trigger apparently because it is connected to an RC bridge which provides a power on reset signal. If you are going to play with the Amiga hardware I strongly reccomend the schematics _from Commodore_ since they are chock full of info. --Chuck McManis uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com These opinions are my own and no one elses, but you knew that didn't you.
grr@cbmvax.UUCP (George Robbins) (07/30/87)
In article <24474@sun.uucp> cmcmanis@sun.UUCP (Chuck McManis) writes: > In article <641@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: > > > >You can order the Amiga schematics from the C-A people in West Chester, PA. > >There is a PAL chip on the drive interface board. It does at least > >three things I know of. > > Huh? In my schematics the 3.5" pcb has a 74LS74 and a 7438, whereas the > 5.25" drive has these plus a 74LS132 and a PST518B (labeled as Q1) it > acts as a schmidt trigger apparently because it is connected to an RC > bridge which provides a power on reset signal. If you are going to play > with the Amiga hardware I strongly reccomend the schematics _from Commodore_ > since they are chock full of info. The PST518 is a clever Japanese power-fail detection device, intended to minimize the possibility that the drive will scribble on your disk if you are so foolish to leave it in the drive when you power off. Apparently, the 3.5" drives are already supposed to contain such circuitry internally. The device is packaged in a 3-lead TO-92 case, meaning it looks an awful lot like a garden variety transistor. -- George Robbins - now working for, uucp: {ihnp4|seismo|rutgers}!cbmvax!grr but no way officially representing arpa: cbmvax!grr@seismo.css.GOV Commodore, Engineering Department fone: 215-431-9255 (only by moonlite)