The strategy is that there are 2 new memory types: far and far const.

The far type is used to define variables stored in RAM. You may have up to about 8 megabytes of variables. Each variable is limited to 64K.

The far const type is used to define variables stored in ROM. These variables may NOT be written to. You may have up to about 8 megabytes. Each variable is limited to 64K.

These variables are accessed using library routines that YOU MUST COMPLETE. The template is found in XBANKING.A51. You will need to complete functions that read and write 1, 2, 3, and 4-byte objects. You will also need to configure the way that the additional memory is accessed.

The complete theory of operation is included in the comments in XBANKING.A51 which may be found in the keilc51lib directory of a standard installation.

Jon Ward
Keil Software