Download the latest binaries from the releases page and place both 'ez80asm.bin' and 'ez80asm.ldr' in the /mos/ directory of your microSD card. This enables the assembler to be loadable as a regular MOS command.

The assembler requires MOS 1.03 at minimum.

ez80asm <filename> [OPTION]
-v List version information
-h List help information
-o Org start address in hexadecimal format, default is 40000
-b Fillbyte in hexadecimal format, default is FF
-a ADL mode 1/0, default is 1
-l Listing to file with .lst extension
-d Direct listing to console

The given filename will be assembled into these files:

• filename.bin -- output executable file
• filename.lst -- output assembler listing (optionally selected by -l flag)

The compiler defaults to ADL=1 mode. This can be overridden using the .ASSUME directive.

The default address is 0x40000.

Lines in the source file should have the following format:

[Label:] [Operator] [Operand] [;Comment]

All fields are optional.

• Labels are defined as first token on a line, terminated by a colon (':')
• Operators are either Assembler directives, or ez80 opcodes. Opcodes without a label should start with whitespace. Assembler directives can start with a dot (.)
• Comments start with a semi-colon (;). A line with just a comment can start without whitespace

Examples

LABEL:                  ; Label without operator
LABEL:LD A,B            ; operator after label without whitespace
LABEL: LD A,B           ; operator after label with whitespace
 LD A,B                     ; operator without label, starting with whitespace
; comment on empty line

Global labels are reachable in the entire source file and cannot have the same name as ez80 mnemonics, nor assembler directives.

Global labels are case-sensitive.

Local labels start with the '@' symbol, terminated by a colon (':') and define a temporary label between two global labels. As soon as a new global label starts, all local labels become out of scope and a new scoped local label space starts.

64 local labels are currently supported in each scope.

Local labels are case-sensitive.

Anonymous labels are labeled '@@', terminated by a colon (':') and define a temporary label. As soon as a new anonymous label is defined, the previous is no longer reachable. Code can use @f/@n or @b/@p, to get the label in the FORWARD/NEXT, or BACKWARD/PREVIOUS direction.

The following formats are supported:

• Hexadecimal - constants starting with 0x, $, or #
• Hexadecimal - constants ending with h
• Binary - constants starting with 0b or %
• Binary - constants ending with b
• Decimal

Examples:

0x0A    ; Hex
$0A     ; Hex
0x0A    ; Hex
#0A     ; Hex
0Ah     ; Hex
0b1010  ; Bin
1010b   ; Bin
%1010   ; bin
10      ; Dec

$ represents the current program counter

Character constants are surrounded by single quotes. Supported escape sequences are:

\n - newline

\r - carriage return

\t - tab

\b - backspace

\\ - backslash

\' - single quote

\" - double quote

Examples:

DB 'a'  ; Defines byte with hex value 61
DB 'B'  ;                   hex value 41
DB '\n' ;                   hex value 0A

Strings are defined as literal characters surrounded by double quotes. The supported character escape sequence constants are supported in strings as well.

Examples:

DB "Test"   ; Outputs hex values 54, 65, 73, 74
DB "Test",0 ; Outputs hex values 54, 65, 73, 74, 0
DB "Test\n" ; Outputs hex values 54, 65, 73, 74, 0A

All assembler directives can be used with, or without leading dot (.)

The 'macro' directive defines a macro, optionally followed by a maximum of 8 arguments. The following lines will be stored as the macro-body, until the 'endmacro' directive is encountered. A macro have to be defined before use.

Macro names have a maximum length of 16 characters.

Example macro definition without arguments:

    macro addhla ; start of macro definition
    add a,l
    jr nc, @1
    inc h
@1:
    ld l,a
    endmacro    ; end of macro definition

Global labels are not allowed in macro definitions, but local/anonymous labels are.

Example macro with arguments:

    macro pointless arg1, arg2
    add a, arg1
    add l, arg2
    endmacro

Example macro usage / expansion later in the code:

    pointless 10, 15
    ; will expand to add a, 10
    ;                add l, 15

• Operators in expressions currently have no precendence other than left-to-right and parenthesis aren't supported yet. So be careful using more than one operator in an expression

While AgonLight is the primary target platform, in order to have easy access to the regular cadre of Unix tools in developing and testing, a small MOS abstraction layer is provided that takes care of abstracting the MOS file API calls to Unix file API calls. This layer also takes care of the differences in file handling and file structures between both platforms.

It appears there is some demand for people to use the assembler on their platform of choice and cross-assemble sources from there to the ez80. I'll not provide direct support for other platforms than Agon, but I have adopted a number of changes to the build scripts, kindly provided by Rob Prouse, to facilitate building on other platforms such as MacOS/Windows. You'll probably see warnings and/or errors on non-Linux builds because I don't test my code on these platforms.