I don't think this exists, but I have a customer who is looking to replace his fairly large 16 bit PIC (256k Flash, 60 I/O) with an MSP430. The one thing he needs but doesn't have is writable EEPROM. Any recommendations?
Hi Amy,
EEPROM is old technology and should be a non-issue. We use small (64B and 128B) 'INFO' flash segments in place of EEPROM, which reduces the cost of manfacturing. Offer the MSP430F5438. This chip provides better performance and much lower power than the PIC device. Futher, the MSP430's superior architecture results in tighter code, hence more efficient use of flash for code space.
Hope this helps.
Regards,
Clark
The MSP430 series can reprogram itself during code execution. So there is no need for a separate EEPROM (which is very costly compared to Flash). All of the MSPs flash memory (if not used for the program itself) can be used for dynamical data storage. For convenience, however, all MSPs have teh mentioned info section which consists of 2 to 4 small Flash segments outside the normal program memory.
There is, however, one thing that's different: while the EEPROM usually can be directly written to more or less randomly, flash cells can only be written to once, then they need to be erasded. So if the program does not sequentially write to the flash space but wants to overwrite/update already written cells, it needs to read the whole flash segment, erase it and write the buffered data back, including the change. This is why the info segments are smaller (64 or 128 bytes) than the program flash (512 bytes).
So maybe the data storage strategy needs to be slightly changes (e.g. fill the segment sequentially, then erase it and begin from start, rather than just writing at the same location all the time).
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Another advantage of the MSP430 is that most of the 16-bit PIC24 depend on an external EEPROM for storing non-volatile data. Besides the obvious penalty of material and processing cost, the external EEPROM is susceptible to noise and have the nasty tendency of clamping down Vcc, preventing the whole system from operating. Another problem is when the I2C package to the EEPROM is not complete with an acknowledgment, a lengthy reset routine becomes necessary to get it back to operation. In that perspective, the erasing of the block before writing to flash is a minor shortcoming easily handled with a well published routine in C (examples readily available in CCS).