useing a 32 pin eprom with the bs2

Comments

• Gadgetman Posts: 2,436

  2006-12-02 22:33 edited 2006-12-02 22:33

  Do you need to use this specific EPROM, or do you just need to access 256KB data?
  (Programming it may be a bit of a trick)
  
  How large blocks of data do you need to access in one go, and how many pins can you set aside for this task?
  
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  Don't visit my new website...
• boeboy Posts: 301

  2006-12-02 22:39 edited 2006-12-02 22:39

  I can use all 16 IO pins and I got it off an old PC motherboard it is a BIOS EPROM and i am just having fun so do not take to much trouble
  
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  lets see what this does... KA BOOM (note to self do not cross red and black)
• Gadgetman Posts: 2,436

  2006-12-02 23:10 edited 2006-12-02 23:10

  Just for fun?
  
  Sounds like a good enough reason to tinker...
  
  
  Lets start with using I/O-pins 0-7 for the databus, then...
  
  Now, the address bus is a bit more difficult, and you probably also want to reserve a pin for the OE signal.
  
  You could hook up a couple of 74HC595 serial-in-parallel-out shift-registers and just clock out new addresses on them. That should be an easy enough way to handle the addresses.
  
  A slightly more difficult way to hook it up, but which will allow you to read out the data quicker is to use a couple of counters.
  Here's a pickture of how a 2764 was accessed on an old PDA.
  http://totallytrygve.com/computer.php?item=1&picture=0&page=2
  
  Use one I/O to reset the counter, then another to clock it until it reaches the address you want.
  (In that particular setup, the I/O-pin used to clock also functions as the A0 signal)
  If the thought of clocking through 256K addresses sounds a bit slow, stick in a 74HC595 or two for the higher addresses, and use them as some sort of 'page address'.
  
  Have fun!
  
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  Don't visit my new website...
• boeboy Posts: 301

  2006-12-03 22:03 edited 2006-12-03 22:03

  Thanks I have a few 74HC595 lying around and a large bread bord now all I need to do is spend forever programing and debugging. lol!
  
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  lets see what this does... KA BOOM (note to self do not cross red and black)
• PJAllen Banned Posts: 5,065

  2006-12-04 01:39 edited 2006-12-04 01:39

  · Mind you, you're on about an EPROM (Erasable) and not an EEPROM (Electrically Erasable.)· So, you can't use it like an NVRAM.· Once·data·is·written at an address, it'll keep that data and cannot be re-written/re-programmed.· You can, of course, read from any address as much as you like.·
  
  · If you want to be able to re-program it, then you'll need to get an EPROM Eraser (uses ultra-violet light.)