mirror of
https://github.com/piotr-wiszowaty/foco65.git
synced 2024-09-27 09:56:23 +00:00
165 lines
2.9 KiB
Markdown
165 lines
2.9 KiB
Markdown
foco65
|
|
======
|
|
|
|
Forth cross-compiler targeting 6502 processors. It needs a 6502
|
|
cross-assembler (e.g. [xasm](https://github.com/pfusik/xasm)) as a backend.
|
|
|
|
Usage
|
|
-----
|
|
|
|
```sh
|
|
foco65 [OPTIONS] INPUT-FILE
|
|
```
|
|
|
|
OPTIONS:
|
|
|
|
-h display help
|
|
-p ADDR,--pstack-bottom=ADDR parameter stack bottom address
|
|
-s SECTS,--sections=SECTS specify comma separated list of sections
|
|
default: init,boot,data,code
|
|
-S INT,--pstack-SIZE=INT parameter stack size
|
|
|
|
Example:
|
|
|
|
```sh
|
|
$ foco65 foo.forth > foo.asx
|
|
```
|
|
|
|
Words
|
|
-----
|
|
|
|
`:` `@` `0=` `1-` `1+` `2/` `2*` `2@` `2!` `and` `c!` `c@` `cmove` `count` `d-` `d+` `d=` `do` `drop` `dup` `i` `j` `loop`
|
|
`+loop` `lshift` `<=` `<` `>=` `>` `-` `+` `or` `over` `rshift` `rsp` `sp` `swap` `unloop` `u<` `u>` `while` `<>`
|
|
`=` `!` `[` `]` `[code]` `[end-code]` `cell` `cells` `not` `[section]` `variable` `2variable`
|
|
`constant` `create` `,` `c,` `,'` `'` `,"` `"` `allot` `lit` `\` `(` `recursive` `[label]` `*` `/`
|
|
|
|
Internals
|
|
---------
|
|
|
|
Type: indirect-threaded.
|
|
|
|
Cell size is 16 bits.
|
|
|
|
Parameter stack pointer is kept in register `X`.
|
|
Parameter stack pointer is decremented before write (stack push) and
|
|
incremented after read (stack pop).
|
|
|
|
Hardware stack (page $01) is used as return stack.
|
|
|
|
Instruction pointer and other work registers are kept in
|
|
page zero occupying total of 12 bytes.
|
|
|
|
After initializing interpreter internal state user-defined word
|
|
`main` is executed.
|
|
|
|
Generated code is placed into sections which are output in the
|
|
order: `init`, `boot`, `data`, `code` or other - specified by the user.
|
|
|
|
Examples
|
|
--------
|
|
|
|
Atari XL/XE executable skeleton. Uses xasm a a backend.
|
|
|
|
<pre><code>
|
|
[section] init
|
|
|
|
[code]
|
|
org $2000
|
|
[end-code]
|
|
|
|
: main
|
|
begin
|
|
...
|
|
again ;
|
|
|
|
[code]
|
|
run boot
|
|
[end-code]
|
|
</code></pre>
|
|
|
|
Atari XL/XE example: display character table as 16x16 array.
|
|
Uses xasm as a backend.
|
|
|
|
<pre><code>
|
|
[section] init
|
|
|
|
[code]
|
|
org $3000
|
|
[end-code]
|
|
|
|
[section] code
|
|
|
|
$230 constant dladr
|
|
|
|
variable screen
|
|
variable cursor
|
|
variable line
|
|
|
|
: cursor-next ( -- u )
|
|
cursor @ dup 1+ cursor ! ;
|
|
|
|
: put-char ( c -- )
|
|
cursor-next c! ;
|
|
|
|
: set-cursor ( u -- )
|
|
screen @ + cursor ! ;
|
|
|
|
: main
|
|
dladr @ 4 + @ screen !
|
|
|
|
0 line !
|
|
16 0 do
|
|
line @ set-cursor
|
|
line @ 40 + line !
|
|
16 0 do
|
|
i j 4 lshift or put-char
|
|
loop
|
|
loop
|
|
|
|
begin again ;
|
|
|
|
[code]
|
|
run boot
|
|
[end-code]
|
|
</code></pre>
|
|
|
|
Atari XL/XE example of defining word in assembly:
|
|
wait for keypress and push the pressed key's code
|
|
on the parameter stack.
|
|
|
|
<pre><code>
|
|
: get-char ( -- c )
|
|
[code]
|
|
lda #0
|
|
dex
|
|
sta pstack,x
|
|
stx w
|
|
jsr do_gc
|
|
ldx w
|
|
dex
|
|
sta pstack,x
|
|
jmp next
|
|
do_gc
|
|
lda $E425
|
|
pha
|
|
lda $E424
|
|
pha
|
|
rts
|
|
[end-code] ;
|
|
</code></pre>
|
|
|
|
Increase cell at the given address. Shows defining words not
|
|
being a valid assembler label.
|
|
|
|
<pre><code>
|
|
create array 16 cells allot
|
|
|
|
: ++ ( addr -- )
|
|
[label] plus_plus
|
|
dup @ 1+ swap ! ;
|
|
...
|
|
array ++
|
|
array 1 cell + ++
|
|
...
|
|
</code></pre>
|