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Hi,
I have recently inherited a project that was originally done using an 8051. A few years ago the hardware was changed to use an 80C251SB but development continued using the C51 compiler.
There is no external data memory in the device. Is it possible to use the 80C251SB's larger internal data memory with the C51 compiler? We have uVision3 with C51 compiler version 8.09.
My bosses want to add PID and serial communication to the device (serial hardware is there but has never been used) and it looks like I've only got about 20 bytes left to work with.
Hi Jack, thanks for the response.
You would probably be best to address the question directly to Keil support for an authoratitive answer.
Keil support tells me that the architecture is too different, and that I need to use the C251 compiler to use that memory.
This is disappointing but not surprising.
from my earlier post: "replacing the discontinued 251 is a no brainer.
Erik
replacing the discontinued 251 is a no brainer.
Yes, it looks like it is easy to replace, just not on the board that I have in front of me. :-)
What would you suggest as a good replacement? I need to suggest something to the bosses.
Yes, it looks like it is easy to replace, just not on the board that I have in front of me
How much boardwork can you do? do you need a specific package? do you need full pin compatibility with the original chip?
I have several suggestions depending on the answers to the above.
If all could change I would go for a PLCC or TQFP chip (maybe even 3V3) to ensure that you did not hit obsolesence again in a short time.
There is resistance to changing anything in the hardware, as the design was outsourced (we don't do any of that here), so it would be least unpopular to suggest something that is pin compatible with the original chip.
What we have is the N80C251SB16 in the 44-pin PLCC package. 5V.
I'm looking through Atmel's website now. There are a lot of options to look at.
Thanks for your help!
Replying to myself (a bad sign)...
Lots to look at, but very little to choose from in the PLCC package. :-(
It looks like I may have to be unpopular.
"It looks like I may have to be unpopular."
Maybe reconsider the option of getting a C251 compiler...?
There is e.g. the P89V51Rx2 which will give you 750 C51 accessible extra bytes of RAM, or be greedy and go for the P89C668 which will give you 8k C51 accessible extra bytes of RAM. Both of these are available in PLCC and are 6 clockers that can double your processing speed with the same crystal, if you change the crystal, you can go to 20MHz @ 6 clocks or 33MHz @ 12 clocks.
the Keil device database
http://www.keil.com/dd/search_parm.asp
Thank you everyone for your suggestions!
I need to talk with my bosses now. The C251 compiler is still an option, as are the replacement chips. I've had feedback from my direct boss (stick with C51, replace the microcontroller) but she won't be making the decision.