A mask ROM is a memory chip which has been given a fixed, unchangeable programming during manufacturing. In the early days of computers these were made of a matrix of small diodes. As I said, the programming of those devices is fixed and there is no risk of it loosing its programmed information - unless it is destroyed e.g. by ESD.
Nowadays I don't think that real mask ROMs are made anymore. It would require the customer to deliver the fixed program code to the chip producer which in turn has to make a lithography mask set for this particular code. The latter process i quite expensive and if a software update would be needed, not only a new mask set would be necessary, but all delivered ROM chips would have to be exchanged for the new ones. It has, on the other hand, been quite common to use EPROMs in black plastic packages as replacement. Compared to the ceramic packages with quartz windows for erasing the chip, the solid plastic package is much cheaper, the chip however can only be programmed once (One Time Programmable ROM, OTPROM). I am quite sure that your chip is one of such. These chips are normally fully pin- and function compatible to their erasable brothers with the 27xxx part numbers. Uwe. Boris Ivic wrote: > > Hi ! I was looking around for the CMOS mask ROM (later I found it's > name) marked MX 23C2100. I looked around Macronix site and found no > datasheet for it. I seems it's production is discountined. As I heavily > depend on it's proper functioning (it is a OS ROM) and my computer is not > getting any younger by the day, I thought it would be a good idea to > have a backup of it. > > But, since I found no other references on the net for 23C2100, I don't > know which (newer) part can replace it. I'm willing to even do some > pin-shuffling with small adaptor-PCB, as long as it can function within > specs of the original (mem size and organization, A0-A16, Q0-Q15, OE and > CE pins). > > Also, I'm not clear on how does the ~BYTE pin work ? Does the mem > organization work as bytes when ~BYTE is low-active or high-inactive ? > > The pdf I gave URL of in previous post has an error on page 2, where > both tables show "~BYTE=VSS" and that's the point of confusion. > > The only real candidate for this is MX 23C4100 (found on Macronix site) > that seems to be an ideal drop-in replacement, but that isn't EEPROM or > FlashROM type. I need EEPROM or FlashROM since : > > 1. It is easier to find > > 2. If I make a mistake it won't be thrown away, just re-programmed again > > Any help is appreciated. > > PS : Feel free to warn Me what does "mask ROM" really means. :-) > > Regards > -- > Boris -- Author: Uwe Zimmermann 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).
