At 2002-08-16 07:23 -0800, Steffen Maisch wrote: >I think, there is no need to back up the content of an MASK ROM in a board. >Because the possibility of being destroyed is not higher than for any other >component. Its content cannot be deleted or altered by reprogramming etc. >But if you want to be sure, the ROM could be read out with any EPROM >programmer that supports 40-pin-chips, and stored as a file. If there were a >problem in future, you could make a new EPROM with this.
I agree. But you don't necessarily need an EPROM programmer. If it's in a simple 64Kbyte computer, just do a memory dump. By the way, I think there were also PROM's in which you would actually blow up the diodes of the cells that you wanted to change from 0 to 1 or 1 to 0. They also wouldn't loose their data over time. As regards masked ROMs: There would indeed be the one-time cost of say $10000 for the mask, but the ROM's would only be say $1 a piece, whereas the EPROM's were very costly to produce being ceramic and having an UV-window, so say $5. Simple math learns that the break-even point is when $10000+n*$1=n*$5, which is when n=$10000/$4=2500. So you would have to buy 2500 ROM's or more to make it profitable to use real ROM's. By the way, also consider the programming costs of (EE)PROM's. This is a relatively slow process, which requires manual labor and is very error prone. I worked until 1997 for the company: http://www.ii.nl/idd/ Already in 1985 it manufactured an EPROM programmer, but in later years also made products that sometimes required to fill 100's of EPROM's. We never bought a gang programmer, but would use several of our own programmers. One person would be busy for a couple of days filling all those EEPROMS. I also sometimes filled EPROM's for a friend who sold second hand PABX's (telephone exchanges for businesses). Terrible work (but it paid well, I think about $0.45 a piece). He would buy a lot of second hand of those PABX's and remove and erase the EPROM's and then have me put in the latest version of the software, but the software would typically be scattered over three EPROM's and the EPROM's would be of all kinds of brands and all require a different burning protocol. I'm quite disciplined, but one time I rather screwed it up. The problem is also that burning an EPROM took a couple of minutes and I tried to program in assembler in between. Greetings, Jaap -- Author: Jaap van Ganswijk INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB CHIPDIR-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
