Problems with erasing AT89S53 chip

[jabela]

Hi, I'm unfamiliar with this hardware so go easy on me

I'm trying to communicate using the AT89ISP cable from Atmel with an AT89S53 chip on a system we have. I'm using the software provided with the cable and a laptop running Win98. (here's the site for it **broken link removed**

I select the port (lpt1), the chip, and the frequency, and then initialize the chip (which works).
If do a blank check on the chip, it says "error, chip is write locked"
If I try to read from the chip, it works, but all I get is a bunch of 00's followed a bunch of FF's repeated over and over.
If I try to autoprogram the chip, it says it successfully erases the chip, but then it says "error, chip is write locked".

I'm under the impression that erasing the chip should remove all locks on the chip and allow me to read/write to it.

Am I doing anything wrong? Any help would be appreciated.
Thanks!

 

[silvio]

software at89s53

As stated too by ISP software LockBit Manager, the current lockbit setttings might not be accurate since the device does not support lockbit mode queries.
Since they can't be queried, in the serial programming mode, the state of the lock bits can only be verified indirectly by observing that the lock bit features are enabled.
That's exactly what you already noticed :

If I try to read from the chip, it works, but all I get is a bunch of 00's followed a bunch of FF's repeated over and over.

Excerpt from data sheet:

Serial Programming Fuse: A programmable fuse is available to disable Serial Programming if the user needs maximum system security.
The Serial Programming Fuse can only be programmed or erased in the Parallel Programming Mode.
The AT89S53 is shipped with the Serial Programming Mode enabled.

Is your AT89S53 purchased from a store or removed from a used board where the manufacturer disabled the serial programming ?
If the first assumption is true, then it's possible to fall into that programming trap even if the ISP software was developed by Atmel:
http://www.atmel.com/dyn/resources/prod_documents/DOC1486.PDF
But if the second assumption is true, then the only solution is to use a parallel programmer and enable the Serial Programming.

BTW, it's needless to upload the files. Rather, you can provides appropiate links to Atmel site.

 

[jabela]

Re: Can't Erase AT89S53

Hi silvio, thanks for the quick reply.

You might be right about the programmable fuse. You see, someone else was working on this before so I am trying to figure out what he was doing. The chip is soldered on to the board and it had a SPI cable port, so I assumed he had been programming it withthat.

From what I can gather it looks like you need to remove the chip from the board to parallel program it. Do you have any recommendations for a good (but not too pricey ) parallel programmer?

Thanks for you help!
~Jon

 

[jabela]

Re: Can't Erase AT89S53

I have a couple more questions.

This is the output I get when I use the Auto Program button.

*** Auto Programming Device ***
Erasing the chip...
Success!

Writing to the chip..
*** Auto Programming Error ***

My question is: If the serial programming fuse is set to disable serial programming, would I still be able to initialize the device? (i am)
Also, would I still be able to erase the device when I select auto program?

Thanks, I'm just want to make sure that the fuse is set before I try any more drastic measures.
~Jon

 

[jabela]

Re: Can't Erase AT89S53

No one has answered my question so I guess I'll clarify it.

Is there a definitive way to find out if the Serial Programming Fuse has been set?
Would I still be able to initialize the target?

Because I can initialize the target and do a Blank Check (it says that the device is write locked). When I try to erase the chip it doesn't seem to have any effect.

Thanks!