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.
