From - Tue Feb 25 22:12:23 1997 Path: jupiter.dnai.com!news.c2.net!re.hotwired.com!news.sprintlink.net!news-ana-7.sprintlink.net!feeder.chicago.cic.net!math.ohio-state.edu!cs.utexas.edu!howland.erols.net!psinntp!news.nstn.ca!tor.istar!east.istar!news1.istar.ca!news From: John Robertson Newsgroups: rec.games.video.arcade.collecting Subject: Identifying PROM's for reading, was Re: Sundance rom images Date: 20 Feb 1997 00:19:42 GMT Organization: John's Jukes Ltd. Lines: 63 Message-ID: <5eg5au$gk5@news.istar.ca> References: <01bc1d64$8d6e9160$6585d9ce@default> <1997Feb17.113842.1@eisner> <01bc1dc1$4296bd40$248fb8cd@default> <5eb7sf$71p@main.freenet.hamilton.on.ca> Reply-To: jrr@flippers.com NNTP-Posting-Host: ts1-15.vcr.istar.ca Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Mailer: Mozilla 3.0 (Win16; I) To: Doug Jefferys Doug Jefferys wrote: > > David Whitman (dwhitman@ix.netcom.com) wrote: > : [re: 9332s] > > Just a public notice to the world that I _think_ I've > done this - the ROMs on my Space Zap were of a strange > configuration, neither 27xx nor 25xx. > > (Translation: Those of you involved, if you've got Space > Zap schems, check 'em. Otherwise, e-mail me so I don't > forget to dig out my old notes. The Sundance ROMs *must* > be preserved!) OK, ok, I hear you troubled folks....the secret of reading unknown PROMS! First, identify if it uses only +5VDC or if it also uses -5 and +12VDC by powering up the game board and doing a check around the PROM on each pin to verify the voltages are +5 or less, but not below 0.00 Vdc. Now that we have the power sorted out, you next need to identify the address and data lines. These are NOT going to be connected to either +5 or Ground, and usually are common between adjacent PROMs, with the JEDEC addressing (like a 2716 or 2764) as the first choice for verifying. Now, if you have found the data pins, which are usually pins 9 - 11 and 13 - 17 and the address pins are 8 - 1 and 23(A8), 22(A9) and sometimes 19(A10) as are standard, you next need to ID the remaining pins. If the device has an number such as XX3X it's probably a 4K device and you are going to look for another address pin. If the number is something like XX1X it's probably a 2K deive and you are left with just the chip selects to ID. Address lines can usually be ID'd by measuring from the CPU's Address pins one at a time to the PROM in question, remembering that not always will the order of the Address lines at the PROM be logical. So now we have up to four leads left to ID. Chip selects can be either relative to grond or to +5Vdc. Pins 18 - 21 are checked as follows...: Pin 18 (19, 20, 21) First, while still in the IC socket on the game board, check with an ohmeter to ground, then to +5vdc bus for continuity. This will probably be a permanent chip select.. Do the same with the other three pins. Now you need to find an IC socket of the Wire Wrap style that has about 2 inch legs. Take a second Wire Wrap socket and bend out the legs 18 - 21Or whichever leads are left) at a right angle and solder each leg to a small DIP Switch bank. Plug the second Wire Wrap socket into the first. Connect a 330 ohm resistor to each of these bent leads and connect the other ends of the resistors to pin 24 (+5Vdc). Now connect the other side of the DIP Switch to pin 12 (Ground). Pop the PROM in question into this hybred, and insert into your eprom reader/burner. Now you can try reading the chips by switching the DIP Switches on and off one switch at a time untill you can read data on your burner! When you are able to read the Data make sure that no other combination of switch settings allows a read (check that the data, if enabled twice, is the same each time), because you may have found another Address line! Clear??? I should draw a picture....\ :-#)# -- (Pinballs, Jukes, Video Games) | John's Jukes Ltd. 2343 Main St. VOICE (604)872-5757 FAX 872-2010| Vancouver, BC, Canada V5T 3C9 e-mail to -> jrr@flippers.com | http://www.flippers.com #(#-: "Old pinballers never die, they just flip out." :-#)#