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+--- Thread: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 (/showthread.php?tid=541)
flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - teletype-guy - 2013-02-18
Hi folks:
I have been using the ds30loader quite happily with two parts: an 18F27J13 and an 18F26K22.
To get ethernet, I was going to use an 18F26K22 with an ENC28J60 chip, but have also been considering an 18F67J60 which builds ethernet into the micro.
- 18F67J60 CONCERNS:
I have not been concerned about flash memory endurance before, but in looking through the 18F67J60 data sheet i saw this note: "The Flash cells for program memory are rated to last 100 erase/write cycles." What? 100-CYCLES? It's 100 minimum and 1000 typical, but sheesh. Not a problem for production, but for development that could mean replacing the TQFP-64 smt chip periodically -- not an easy task. Also not a thing mentioned by makers of some dev boards (eg: olimex, ccs) but I have since found that at least dangerousprototypes is cool enough to warn folks about it. I may skip this chip for this 100-cycle programming limit -- I'll bet a lot of folks have dying dev boards and no idea why.
>>> DOES ANYONE HAVE ANY INPUT ON USING THIS CHIP?
- 18F27J13 CONCERNS:
In the datasheet for the 18F27J13 I use, it says 10,000 program cycles minimum (search for "endurance"), however, I also see this programming note (this note is also on the 67J60 datasheet, but not the 26K22):
"1: Unlike previous devices, the PIC18F47J13 family do not reset the holding registers after a write occurs. The holding registers must be cleared or overwritten before a programming
sequence. 2: To maintain the endurance of the program memory cells, each Flash byte should not be programmed more than once between erase operations. Before attempting to modify the contents of the target cell a second time, an erase of the target page, or a bulk erase of the entire memory, must be performed."
When loading a chip with the pickit3, I can erase before load (also something I never thought about before), but when using a bootloader, the responsibility lies in the BL firmware.
>>> DOES THE ds30loader MEET THESE PROGRAMMING REQUIREMENTS?
- 18F26K22:
It has 10,000 program cycles minimum and no special program notes.
Any comments appreciated. Just trying to select good parts.
gil smith
RE: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - Mikael Gustavsson - 2013-02-18
You are welcome to post here but I think you will have a better chance for response in the Microchip forums.
RE: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - teletype-guy - 2013-02-18
Well, fair enough that the question of programming cycles on a pic is a bit off-topic on the bootloader forum, though I think it is important that folks here know that a popular microchip part has such a very low program cycle (from parts that we are used to having 10,000 cycles guaranteed, to only 100 cycles on the 67J60) -- it makes me nervous from a reliability standpoint (their claimed flash retention also dropped from typical 20 years to 10, so they are cutting corners somewhere in their flash silicon, IMHO).
But what about my question about the programming note I found in the datasheets for the two "J" parts?:
"To maintain the endurance of the program memory cells, each Flash byte should not be programmed more than once between erase operations. Before attempting to modify the contents of the target cell a second time, an erase of the target page, or a bulk erase of the entire memory, must be performed."
Does the bootloader do an erase before program, to keep these J chips happy?
thanks,
gil
RE: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - Mikael Gustavsson - 2013-02-18
Yes ds30 Loader always erases before programming.
RE: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - teletype-guy - 2013-02-19
Thanks Mikael. Love the loader.
RE: flash memory cycles and 18F67J60, 18F27J13, and 18F26K22 - Mikael Gustavsson - 2013-02-20
Thanks
