The assembler supports several modifiers when using symbol addresses in 68HC11 and 68HC12 instruction operands. The general syntax is the following:
%modifier(symbol) |
This modifier indicates to the assembler and linker to use the 16-bit physical address corresponding to the symbol. This is intended to be used on memory window systems to map a symbol in the memory bank window. If the symbol is in a memory expansion part, the physical address corresponds to the symbol address within the memory bank window. If the symbol is not in a memory expansion part, this is the symbol address (using or not using the %addr modifier has no effect in that case).
This modifier indicates to use the memory page number corresponding to the symbol. If the symbol is in a memory expansion part, its page number is computed by the linker as a number used to map the page containing the symbol in the memory bank window. If the symbol is not in a memory expansion part, the page number is 0.
This modifier indicates to use the 8-bit high part of the physical address of the symbol.
This modifier indicates to use the 8-bit low part of the physical address of the symbol.
For example a 68HC12 call to a function foo_example stored in memory expansion part could be written as follows:
call %addr(foo_example),%page(foo_example) |
and this is equivalent to
call foo_example |
And for 68HC11 it could be written as follows:
ldab #%page(foo_example) stab _page_switch jsr %addr(foo_example) |