Status: Assigned
Owner: sebastien.lelong
Labels: Type-Enhancement Priority-Medium Component-Device
Component-Peripheral
New issue 154 by sebastien.lelong: USB RAM locations (BDT & Data)
http://code.google.com/p/jallib/issues/detail?id=154
USB RAM is divided into 2 main areas:
- BDT (Buffer Descriptor table)
- USB data (actual buffers)
Current USB implementation uses USB_BASE_ADDRESS variable as the beginning
of USB RAM, assuming it's the first area, BDT. For instance, 18F14K50 USB
RAM starts at 0x200h, 18F4550 at 0x400h. From this reference point are
declared buffers and other USB specific variables. This highly important
variable is declared in usb_defs.jal.
For now, "if then else" logic is implemented to set this variable according
to target chip. There's no information about how USB RAM is structured in
device file. If we had this information, we could enrich this "if then
else" logic to support, possibly, all USB PIC.
Is it possible to include, in device files:
1. the start of BDT address ? (0x200h to 0x27Fh for 18F14K50, 0xD00h to
0xDFFh for 18F27J53)
2. USB data locations ? (0x280h to 0x300h for 18F14K50, 0x060h to 0xCFFh
and 0xE00h to 0xEBFh for 18F27J53)
See page 258 for 14K50 and page 387 for 27J53 for memomy space.
1. would help setting USB_BASE_ADDRESS in usb_defs.jal in a more generic
way.
2. really is an extra, using this type of information would require huge
modifications in libraries. But also would allow to build heavy USB device.
I'm not sure it's useful right now though...
Seb
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