Rob, this is strange because PIC18f67j50 (USB PIC) datasheet says 3904 bytes ram, and compiles with 3808 ram. Only 96 bytes difference, unlike 18f4550/18f4455
Matt. On Dec 3, 3:17 am, Rob Hamerling <[email protected]> wrote: > Hi Matt, > > On 2010/12/03 04:50, mattschinkel wrote: > > > Sorry, I was just looking at the datasheet for 18F4455. The datasheet > > says 18F4455 and 18f4550 both have 2048 bytes ram, but when I compile > > the blink samples it only says 928 bytes. This is not enough for the > > fat32 lib. > > > Does someone here know why some ram is not usable? is it because of > > USB? > > The 4 banks you are missing (GPR4..7) are for use by the USB module when > is is active, but are availabe as 'normal' RAM when the USB module is > inactive. > > The available RAM of a device as specified in the Jallib device files is > obtained from the .lkr file (in /MPASM SUITE/LKR). In the file for the > 18F4455 banks GPR4..7 are marked PROTECTED, which is always interpreted > (by the dev2jal script) as unavailable for normal use. > The device file is static, it cannot dynamically change the amount of > RAM based on the situation if the USB module is active or not. > Since a PIC like the 18f4455 will normally be used with USB active I > think that hiding these 4 banks for the user is the best choice. > > Regards, Rob. > > -- > R. Hamerling, Netherlands ---http://www.robh.nl -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
