N82S129AN reader. how to?

[neazoi]

hello I need to read the program inside a N82S129AN?
please help

 

[betwixt]

That's an old one! I haven't used on of those in maybe 20 years.

You can read it just like a static RAM, make the CE pin low and put the address on the input pins, the outputs will show the 4-bit data. It is fully static so you don't have to worry about timing or clock signals.

Brian.

 

[neazoi]

That's an old one! I haven't used on of those in maybe 20 years.

You can read it just like a static RAM, make the CE pin low and put the address on the input pins, the outputs will show the 4-bit data. It is fully static so you don't have to worry about timing or clock signals.

Brian.

Ok, so I will be probaly be able to replace it with an EPROM if I read it's program the way described?
Any ideas about which eprom to use?

 

[betwixt]

It might be tricky. The 82S129 has a 50nS access time which is faster than many EPROMs so if you are using it in a critical application you may not have enough speed. If the speed isn't important you can use almost any EPROM, only 256 addresses and 4-bits are used so even the smallest modern EPROM will have many times more capacity than you need. Use whichever is easiest for you and tie any address lines higher than A7 to ground and program the upper 4 bits of data to zero between addresses 0 to 256.

Brian.

 

[neazoi]

It might be tricky. The 82S129 has a 50nS access time which is faster than many EPROMs so if you are using it in a critical application you may not have enough speed. If the speed isn't important you can use almost any EPROM, only 256 addresses and 4-bits are used so even the smallest modern EPROM will have many times more capacity than you need. Use whichever is easiest for you and tie any address lines higher than A7 to ground and program the upper 4 bits of data to zero between addresses 0 to 256.

Brian.

It has been used in a PC-XT 8088 clone motherboard and I would like to replace it with a more "standard" part.
(actually a crazy thought to re-clone it )

 

[betwixt]

It depends on what it does on the board. On some clones they were used as a bus command decoder instead of Intels 8288, if that is the case the speed is critical and an EPROM will not work. If it is used as a peripheral address decoder you might be better to consider either a TTL decoder (74LS138 style) or a PAL, both will work at much higher speed than an EPROM.

Back many years ago the AMD data book for the 8088 had a design for a PAL based version of the 8288. Unfortunately, (really bad timing) I took a car load of data books, including that one to a paper recycling center last week. I'm moving home shortly and needed to clear a lot of space so hundreds of data books had to go!

Brian.

 

[neazoi]

It depends on what it does on the board. On some clones they were used as a bus command decoder instead of Intels 8288, if that is the case the speed is critical and an EPROM will not work. If it is used as a peripheral address decoder you might be better to consider either a TTL decoder (74LS138 style) or a PAL, both will work at much higher speed than an EPROM.

Back many years ago the AMD data book for the 8088 had a design for a PAL based version of the 8288. Unfortunately, (really bad timing) I took a car load of data books, including that one to a paper recycling center last week. I'm moving home shortly and needed to clear a lot of space so hundreds of data books had to go!

Brian.

Thanks Brian. I have no idea for the reason that it is used on the motherboard, but if an eprom is to be used, I will try these high speed eproms from WSI, not the old ones. These "new" eproms have access times as low as 25-45ns. i do not know if it would be enough for the application.
The other thing I was thinking, why not using a static ram instead like the MS62256J-15NC with fast 15nS access time and maybe a battery to make it non-volative?

 

[betwixt]

It should work but it would be massive 'overkill' to use a 256K bit memory as a replacement for a 256 bit one!.

It might be easier to use a PAL, it would be as fast as the original and smaller then an EPROM type device.

Brian.