EPROM Question...

[lord loh.]

I hope this is the right forum to ask this sort of a question....

I read a particular term in the datasheet of 27256 EPROM...
It said, 168±8 burn-in (125°c)hr what does this mean ?

Also, I would like to know if an EPROM requires UV light during the programming or only during erase operations.

Is there a limit on the number of times an EPROM may be programmed ?


And last, Can an EPROM be programmed on a bread board ? by constantly changing connections, and giving the final puse of Vcc/Vpp and chip select ?

Thanks in advance...

 

[bmcculla]

It sounds like you would be better off using Flash. Flash is a more modern Programmable, erasable memory. It doesn't need UV light to erase and most new chips only require a standard digital supply to program - no high programming voltages required. Digikey.com has tons of flash devices to choose from. EEPROM is similar to Flash.

Burn in usualy means that they have run the part in a very hot enironvent to make sure it doesn't fail.

 

[Oznog]

Also, I would like to know if an EPROM requires UV light during the programming or only during erase operations.

Is there a limit on the number of times an EPROM may be programmed ?


And last, Can an EPROM be programmed on a bread board ? by constantly changing connections, and giving the final puse of Vcc/Vpp and chip select ?

Yeah, you want EEPROM.
EEPROM can be reprogrammed only a limited number of times. but it's a very large number. Check your spec sheet. If you were so paranoid about power loss that you constantly wrote EEPROM as fast as the system allowed so you could restore it at any point, you might run into long-term reliability problems associated with exceeding the rated number of cycles.

You might be able to program it with switches, but there is no practical use in doing so. A microcontroller works quite effectively.

 

[lord loh.]

Burn in usualy means that they have run the part in a very hot enironvent to make sure it doesn't fail.

You mean the programming is to be done at 125°c....But what about the hour part ? 168±8 ....It seems to me that it can be programmed only for a limited number of hours...and depending on the speed of the programmer, it might mean ~ 700 times....(assuming 4096 bytes each requiring 200ms pulse)

Tell me - am I wrong ?

You might be able to program it with switches, but there is no practical use in doing so. A microcontroller works quite effectively.

I have to write a minimal monitor for my first 8085, and have got a 5v source, 8085, ram chip and plan to buy a EPROM chip...So my first programme must be via switches or worse...by pulling wires in and out of the breadboard (nightmare!!)

If I choose an EEPROM, does it become any different to interface it with an 8085 ?
And I still want to know if UV light is needed during the programming...[/code]

 

[Nigel Goodwin]

Burn in usualy means that they have run the part in a very hot enironvent to make sure it doesn't fail.

You mean the programming is to be done at 125°c....But what about the hour part ? 168±8 ....It seems to me that it can be programmed only for a limited number of hours...and depending on the speed of the programmer, it might mean ~ 700 times....(assuming 4096 bytes each requiring 200ms pulse)

Tell me - am I wrong ?

You might be able to program it with switches, but there is no practical use in doing so. A microcontroller works quite effectively.

I have to write a minimal monitor for my first 8085, and have got a 5v source, 8085, ram chip and plan to buy a EPROM chip...So my first programme must be via switches or worse...by pulling wires in and out of the breadboard (nightmare!!)

If I choose an EEPROM, does it become any different to interface it with an 8085 ?
And I still want to know if UV light is needed during the programming...[/code]

UV is never needed for programming, only for erasing UV eraseable EPROM, an EEPROM is electrically eraseable (what the first two E's stand for) - so you don't require one at all for EEPROM.

You can buy EEPROM replacements for EPROM's, they drop directly in the same socket - and avoid the extremelyslow UV erasure process.

Ignore all the burn-in specs, you don't need to know anything about them, all you do for an EPROM is set the address and data lines to the values you require, then apply the correct length pulse (or pulses) to the programming pin - the voltage required depends on the specific part, but is usually in the 20-30V range.

If you've got to do this without a programmer it's going to take you a HUGE amount of time, and give massive potential for mistakes - and you've still got to built some hardware to generate the programming pulses. I suggest you do a web search for EPROM programmers, there are various PC based parallel port designs, that don't require anything programming to use them.

Even if you can't find a design you like, it would probably be faster to design and build your own than program by hand on a breadboard.

 

[lord loh.]

Yes, I have decided to build my own. I plan to give pulses of the duration using 555 timer ICs.

Now the datasheet of my ROM says that I can give a 1ms pulse and see if the data is burnt in. if yes, a 3ms pulse to over programme it.

If the data is not burnt in, I redo the 1 ms programme (repeat till programmed max 25 times). Then give n*3ms pulse of Vpp. Where n is the number of 1ms pulses applied.

If 25 1ms pulses are applied and the data does not burn in, the flowchart says failed.

What does this mean ? I throw the device, or UVErase it and reprogramme ?

 

[Nigel Goodwin]

Yes, I have decided to build my own. I plan to give pulses of the duration using 555 timer ICs.

Now the datasheet of my ROM says that I can give a 1ms pulse and see if the data is burnt in. if yes, a 3ms pulse to over programme it.

If the data is not burnt in, I redo the 1 ms programme (repeat till programmed max 25 times). Then give n*3ms pulse of Vpp. Where n is the number of 1ms pulses applied.

If 25 1ms pulses are applied and the data does not burn in, the flowchart says failed.

As you can imagine from the process required, it's not a very practical manual process - I would suggest you use either a computer, mico-processor, or micro-controller to program your EPROM's.

You could probably design, built, and test, a programmer in the time it would take you to manually program more than a few bytes.

What size EPROM's are you looking at?.

What does this mean ? I throw the device, or UVErase it and reprogramme ?

Programming an EPROM simply sets 'ones' to 'zeros', any bits that are 'ones' don't need programming.

When you erase an EPROM all the bits are set to 'ones', so I don't see how erasing it (when it's already erased) is going to help. But I suppose it's worth a try - if you ever happen to be in that situation.

 

[lord loh.]

...But I suppose it's worth a try - if you ever happen to be in that situation.

The situation when my device fails ? ie to say that the device is unprogrammable even after 25 Vpp pulses ?

How often does this happen ? Will this happen on new EPROM devices (first time programme) or on subsiquent erase-reprogramme cycles...

What is the reason for the failure ? improper erase? or silicon level defect ?

 

[Nigel Goodwin]

...But I suppose it's worth a try - if you ever happen to be in that situation.

The situation when my device fails ? ie to say that the device is unprogrammable even after 25 Vpp pulses ?

How often does this happen ? Will this happen on new EPROM devices (first time programme) or on subsiquent erase-reprogramme cycles...

What is the reason for the failure ? improper erase? or silicon level defect ?

EPROM's are only specified for a limited number of erase and reprogramming cycles, presumably it's when that has been exceeded?.

It's not something I've ever seen, I've never programmed many EPROM's, and it's even less likely now as they are pretty well obselete technology.

As you've not even attempted to program one yet, it seems rather silly to be worrying about it :lol:

 

[lord loh.]

:cry: I am worried because an EPROM costs Rs 95/- in India (1us$~Rs50)

May sound cheap but Rs 95/- is a lot. I spend ~$30 for a whole month of meals....My father is going to bang me if I start purchasing EPROMs every alternate day...So I have to be damn sure of what I am doing...

 

[Nigel Goodwin]

:cry: I am worried because an EPROM costs Rs 95/- in India (1us$~Rs50)

May sound cheap but Rs 95/- is a lot. I spend ~$30 for a whole month of meals....My father is going to bang me if I start purchasing EPROMs every alternate day...So I have to be damn sure of what I am doing...

As you've not filled your location in, we didn't have any idea where you might be!, but generally you can find EPROM's in quite a lot of old equipment - very old computer motherboards had them in, and so do some oldish TV's.

What are you trying to do with them anyway?, and what size ones are you wanting? - bear in mind that various different EPROM's require slightly different programming methods and voltages.

I would suspect your main cause for concern is damaging the EPROM by an incorrect programming process?.

As far as I'm aware though they are fairly sturdy devices.

 

[lord loh.]

I live in India...I shall fill it in...

I purchased a 4Kb ROM and want to try make my first computer (8085)

I have viewed the datasheet and the programming techinique is trickey...

 

[Nigel Goodwin]

I have viewed the datasheet and the programming techinique is trickey...

You might try looking at , which is a file I downloaded years ago about making an EPROM programmer.

It's not my design, and I've never used it, but it comes complete with PC Pascal source code, and might be useful to you?.