It took me a little while to figure out why my bank wasn’t running. asm(“call 4030”) does not output machine code that jumps to 0x4030–it jumps to 4030 or 0x0fbe. That’s wrong. So I added in the “0x” and all was well.

So now I am starting to wrap up a refactoring exercise.

I added a block that will go in all 16 sections. Each will have a pointer at 0x0026 that will point to this block.

 1 #define BANKINFO_TYPE_UNKNOWN ((uint8_t)0x00)
 2 #define BANKINFO_TYPE_CVECTOR ((uint8_t)0x01)
 3 #define BANKINFO_TYPE_APPLET ((uint8_t)0x02)
 4 #define BANKINFO_TYPE_EXECUTABLE ((uint8_t)0x03)
 6 // Every bank has a pointer at 0026 that points to a const BankInfo* _BANK_INFO; both crt0.s and crt1.s
 7 // expect a _BANK_INFO to be defined. This will typically be where main is defined.
 9 typedef struct BankInfo {
10     uint16_t CVersion; // 0{ix} 1(ix)
11     const char* Name; // 2{ix} 3(ix)
12     const char* TimeStamp; // 4{ix} 5(ix)
13     uint8_t Flags; // 6{ix}
14     uint8_t Type; // 7(ix) 1=c vector, 2=applet, 3=bank
15     uint16_t W0102; // 8{ix} 9(ix) // valid only is this is 0102
16     uint16_t W0304; // 10{ix} 11(ix)
17 } BankInfo;

This will be used for listing the contents of the flash. There will be 3 types of flash banks:

  • C Vector: These have the C library and drivers that the applets can use. But they don't really need anything else.
  • Applet: These will run the programs that I want to run
  • Executable: These will run standalone programs or menu items.

The applets require that they are linked with crt1.rel. The others with crt0.s. The C vectors need to link in c_vector.c.

At this point, I have to start reserving certain banks: 00: flash bank 0 is always run from reset. It will have a standalone executable with complex menu, but no c vector 01: flash bank 1 is always in bank 1 from reset. It will always be available for bank 00 to be able to hold programs larger than 16K. 10: RAM bank 10: This will be placed in bank 2 (i.e. 0x8000-0xbfff). It is there by default 11: RAM bank 11: This will be placed in bank 2 (i.e. 0xc000-0xffff). It is there by default

12: RAM bank 12: RAM bank 12 will be the standard bank for run from RAM in bank 0 (i.e. 0x0000-0x3fff)
13: RAM bank 13: RAM bank 13 will be the standard bank for run from RAM in bank 1 (i.e. 0x4000-0x7fff)
14: RAM bank 14: will be used for the standard bank that holds the C vector (0x0000-0x3fff)
I had to deal with the fact that the BankInfo block may be placed in blocks other than the block it expects, so the pointers to strings also have to point to the proper location.
All this bank switching has my brain running in circles, but it's finally getting into shape.