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asm2 is a native 1802 Elf-OS assembler updated for Elf-OS 0.4.0
The source file extension must be .asm but the file extension is not used when invoking the assembler.
For example, asm2 test compiles the source file test.asm
The -5 command line switch allows support of 1804/1805/1806 op codes
Upon completion of assembly, asm2 produces a .obj file. link2 is required to convert the .obj file to a binary file with the default file name being a.out
Assembler Line Format:
label: OPCODE ARGUMENTS ; Comments
Labels and comments are optional, and not all opcodes have arguments. In
addition to the 1802 instruction set, Edt/Asm provides 5 pseudo-opcodes:
  ORG   addr Specify address for assembly
  DB      b1,b2, Define a list of bytes in memory
  DB      'c1','c2'...'cn' Define a list of chars in memory (for example, 'A')
  DW     w1,w2,...wn Define a list of words in memory
  DS      n Define storage without assigning a value
  END    start End of assembly, also specifies a start address
LABEL: EQU n Value of n is in decimal or hex
Where addr,bn,wn can be a hex value such as 8000h or a decimal value such as 256.
A colon (:) is used to delimit a label.
Example Elf-OS restart program
F_MSG:     EQU 034Bh   ; ELF-OS message vector
F_WARM: EQU 0FF00h ; BIOS warm start vector
                  ORG 2000h  ; start of program load address
                   BR START   ; branch around header
                   DB 88h         ; 8th month-upper bit indicates extended hdr
                  DB 14            ; the 14th day of the month
                  DW 2021       ; the year
                  DW 7              ; indicate that this is build 7 of the program
                  DB 'BJM'         ; text for the Elf OS version command
                  DB 0               ; indicate end of ASCIIZ text string
START:      SEP R4           ; call to output msg to terminal
                  DW F_MSG    ; elf OS output msg address
                  DB 'Rebooting Elf-OS ...',0
                  LBR F_WARM   ; branch to entry point of EPROM
                  END START   ; indicate the entry point for the program
asm2 currently supports simple arguments as well as some arithmetic expressions. For example:
  LBR  010h+START and START:  LDI  2+4*5 are supported.
    LBR   START+010h causes an assembly error.
When specifying registers, the register number may (but need
not) begin with R, for example: LDN R8
The high byte of a value can be obtained by adding .1 to the end of a label,
for example: LDI STACK.1 will load the high byte of the address of
STACK. .0 will obtain the low byte of a value, for example: LDI STACK.0