512 byte arrays - C18?

[futz]

BoostC won't do 512 byte arrays. It's limited to 256 bytes. For my 18F4620 SD Card project I want to do 512 byte blocks without a bunch of overhead to split the reads/writes.

Can I do it if I change compilers? Maybe C18? PICC? C30 (I could change chips)?

 

[Nigel Goodwin]

How much RAM does the 18F4620 have?, big buffers are always a problem on PIC's.

 

[futz]

How much RAM does the 18F4620 have?, big buffers are always a problem on PIC's.

Almost 4K, but it's in 256 byte banks.

I could code up a little thing to split it, but if C18 will do it for me without that extra work... well, I've been meaning to give it a test anyway. If it won't do it I may as well stay with BoostC.

 

[donniedj]

Futz, If I remember correctly you have just ventured into the 18F family? I also thought you started to use 16-bit micros. Any reason for not using a 16-bit micro? With the 16-bit chips Banks are eliminated and all the problems associated with them. 24FJ64GA002 is an equivalent chip minus EEPROM.

 

[futz]

Futz, If I remember correctly you have just ventured into the 18F family? I also thought you started to use 16-bit micros.

Umm... Not really. I ventured into 18F's many years ago when they were something new. I have tons of different PICs. My reason for using the 4620? I threw a dart. I had it. Hadn't used it yet. "Ok, that's the one I'll use."

I'm kind of schizo in my "studies". This is just a hobby for me, not a job. Nor am I in school. It's just for fun. I jump around to whatever interests me at the moment. I can be very focused on one thing for a while and then another shiny thing distracts me and I'm off on something else.

Any reason for not using a 16-bit micro? With the 16-bit chips Banks are eliminated and all the problems associated with them. 24FJ64GA002 is an equivalent chip minus EEPROM.

No good reason at all. I have a 24F that I should have used, but where's the challenge there? It's already 3.3V.

 

[Mike - K8LH]

Futz,

I seem to recall this subject coming up on Forum.Microchip several times but I haven't had the need with C18 yet so I don't remember the solution. Might be worth a search at Forum.Microchip for you though.

Mike

 

[Pommie]

I think you are limited to 256 byte arrays in C18. There may be some magic that can be performed with the linker script but, if there is, I don't know it.

Mike.

 

[futz]

I seem to recall this subject coming up on Forum.Microchip several times but I haven't had the need with C18 yet so I don't remember the solution. Might be worth a search at Forum.Microchip for you though.

Ya, I grabbed C18 and did a bit of reading of the manual. But then I had to do some real work and haven't had time to pursue it. Tonight for sure...

 

[futz]

I think you are limited to 256 byte arrays in C18. There may be some magic that can be performed with the linker script but, if there is, I don't know it.

You could be right. C30 does do 512's though, cuz the book I'm stealing code from does 512 byte arrays and it's a PIC 24F and C30 book.