Where should I discuss SD/MMC FAT issues?

[JD123]

I'm trying to avoid this huge 512 byte array, which won't fit on this PIC anyway.

Speaking of the PIC, I was at the store today and picked up an 18F2050. It's not a 2025, but it should do. I loose one CCP but gain a USB. Past that I can't tell them apart.

[skimask]

I'm trying to avoid this huge 512 byte array, which won't fit on this PIC anyway.

Speaking of the PIC, I was at the store today and picked up an 18F2050. It's not a 2025, but it should do. I loose one CCP but gain a USB. Past that I can't tell them apart.

2050? Maybe a 2550...
Should do just fine. Combine that PIC with the examples from Mr.E's USB demo in another thread (or the config bit hassle that WILL follow...just seems to happen that way), and you'll be in great shape.

And the 512 byte array won't fit, but the 32 byte or 64 byte array of the EEPROM page will...

[JD123]

{getting out my reading glasses...} Yup, it's a 2550.

I don't see a "MrE, Mr. E, Mr.E or Mr E" in the member list???

[skimask]

I don't see a "MrE, Mr. E, Mr.E or Mr E" in the member list???

http://www.picbasic.co.uk/forum/show...ghlight=mister

I got this one in my hotlinks...

[JD123]

Thanks. That's a thread I wish I was around for back in 06.

[JD123]

Something is wrong with my Tcy counter. It must be rolling over. I didn't make provisions for it rolling over because I couldn't imagin it taking more than 65K Tcy to move the data off the MMC and onto the F-RAM. I guess I was wrong... very wrong.

Best condition Tcy's to move data:

gosub to MMC read - 2Tcy

get byte - 24Tcy (3Tcy per bit)

return - 2Tcy

gosub to write F-RAM - 2Tcy

write F-RAM - 117Tcy (13Tcy per bit (min. clock delay 5Tcy), 9 bits w/ack)

Ack overhead - 9Tcy if tested, 3Tcy if blind read

return - 2Tcy

total for single byte loops - 158Tcy

repeat 512 times - 80,896Tcy

I must be moving data WAY slower than I thought. Time to detect TMR1 rollover and see what it really is.

[skimask]

Something is wrong with my Tcy counter. It must be rolling over. I didn't make provisions for it rolling over because I couldn't imagin it taking more than 65K Tcy to move the data off the MMC and onto the F-RAM. I guess I was wrong... very wrong.

Make an interrupt for the overflow interrupt and increment another word based on that.
Also, I was looking thru your code again.
Whenever you multiply or divide by a power of 2, you can easily use a shift to accomplish the same thing. Saves a bunch of cycles, and some code space.
For instance, you've got:
OP = OP * 512 (at least 9 shifts, 9 double word adds + carry's, probably 100-ish cycles)
That can be rewritten:
OP = OP << 9 (9+ cycles)

repeat 512 times - 91,136Tcy

Put some of your shorter Gosub/Returns in-line with the loop that runs 512 times. For each Gosub/Return you eliminate in the loop, you save at least 2,048 cycles (about 2% for each one).