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zasm - Z80 Assembler – Version 4.0

Pseudo instructions

.phase and .dephase

    .phase <address>
    ...
    .dephase

This Pseudo instructions
8080 Assembler: 8080 pseudo instructions
pseudo instruction Pseudo instructions: defl, set and '='
Labels: SET
sets the logical origin for the following code to the new address. The new logical origin is valid until the .dephase instruction resets it to the physical origin or another .phase instruction Pseudo instructions: defl, set and '='
Labels: SET
sets it to another value. (note: in zasm v3 'org' was used to change the logical origin.)

The logical code address is what you mostly work with. E.g. Types of labels: Program labels
Types of labels: Program labels
program labels and '$' refer to the logical code address. This logical code address can be moved with .phase and .dephase.

The physical code address is the address at which the code stored by the assembler is supposed to be visible to the cpu. (At least it should be.) Because most code is executed where it was stored (which means: it was not copied somewhere else in ram before it is executed there) the physical and the logical address are most times the same.

.phase and .dephase are typically used Assembler directives: #if, #elif, #else, #endif
Pseudo instructions: if, endif
if some portions of code are copied from rom into ram, where it can be modified by the running program.

In case you need to access the physical address of the code at a position where you have shifted the logical address with .phase you can use '$$' instead of '$'.

Note: the physical code address is biased to the 'org' address resp. to the start address of the current Assembler directives: #code
Including C Source Files: #code
#code or Assembler directives: #data
Including C Source Files: #data
#data segment, not the start of the eprom!

Example: relocated jump table

In this #insert: Examples:
#assert: Example:
incbin: Examples:
example a jump table is copied from rom to ram, either to assert fixed addresses or to allow the running program to patch some entries:

            ...                 ; some code
            ccf
            ret

            .phase  $FE00       ; shift origin
rom_table:  Pseudo instructions: equ
Types of labels: Named values
Labels: EQU
equ $$ ram_table: Pseudo instructions: equ
Types of labels: Named values
Labels: EQU
equ $ putchar: jp putchar_rom puttext: jp puttext_rom getchar: jp getchar_rom getline: jp getline_rom table_size: Pseudo instructions: equ
Types of labels: Named values
Labels: EQU
equ $ - ram_table .dephase ; back to physical code address gizmo: ld de,ram_table ld hl,rom_table ld bc,table_size ldir ld a,0 ; more code ...

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