en:pfw:assemblers_rp2040-assembler
Table of Contents
Assembler for RP2040
The idea
A compact Forth-style macro assembler with an efficient literal pool mechanism for the RP2040.
A Forth-style assembler uses all the capabilities of the Forth interpreter and assembles opcodes in between.
An example:
code SQUARED ( +n -- +n^2 ) tos tos muls, next, end-code
Implementation
The example code asumes a 32-bit machine that has 16-bit & 32-bit compile actions.
It is also asumed that the code runs in RAM as noForth T on the RP2040 does.
Because the Thumb-2 opcodes of the ARMv6-M use a RISC like architecture, macros
are added to make assembly a bit more easy.
An implementation example for CODE
and END-CODE
is showed too. Missing words in Generic Forth are:
(* ( "ccc" -- ) - Skip all text until *) is found +TO ( n "name" -- ) - Add n to the contents of the value "name" VOCABULARY ( "name" -- ) - Define a named wordlist
All Thumb2 instructions
✦ Two low register opcodes ands, eors, adcs, sbcs, rors, tst, neg, cmn, orrs, muls, bics, mvns, sxth, sxtb, uxth, uxtb, rev, rev16, revsh, lsls, lsrs, asrs, movs, cmp, ✦ Two all register opcodes add, mov, cmp, ✦ Three low register opcodes adds, subs, str, strb, strh, ldrb, ldrh, ldr, ldrsb, ldrsh, ✦ Two low register & 3-bits immediate adds, subs, rsbs, ✦ Two low register & 5-bits immediate lsls, lsrs, asrs, str, strb, strh, ldr, ldrb, ldrh, ✦ One low register & 7-bits immediate (RP-specific) add, subs, sub, ✦ One low register & 8-bits immediate movs, cmp, str, (rp) ldr, (rp) ldr, add, (rp) push, pop, bkpt, udf, svc, adr, stm, ldm, adds, subs, ✦ Various 16-bit opcodes noop, nop, yield, wfe, wfi, sev, cpsie, cpsid, bx, blx, ✦ Fourteen jump instructions =? cs? neg? vs? u>? <? >? no ✦ Control structures if, else, then, ahead, begin, while, repeat, again, until, ✦ Literal pool additions ALIGN, CODE> POOL, APOOL, ## ✦ Assembler macros ALIGN, ## POOL, APOOL, )+ -) NEXT,
Two usage examples
code LSHIFT ( x1 +n -- x2 ) day tos movs, \ 1 - +n to DAY tos sp )+ ldr, \ 2 - pop X1 to TOS tos day lsls, \ 1 - Shift TOS DAY positions left next, \ 6 end-code code KEY?) ( -- f ) 40034018 , \ UART0 UARTFR code> sun w ) ldr, \ Read UARTFR to SUN tos sp -) str, \ Push stack tos sun ) ldr, \ Read flags tos 1B # lsls, \ Build flag out of bit-4 tos 1F # asrs, \ Extend sign tos tos mvns, \ Invert flag next, end-code
File name | Purpose | in Dropbox (external link) |
Thumb assembler doc v2.pdf | Documentation | Assembler documentation |
RP2040-asm uni.f | RP2040 assembler | noForth RP2040 assembler |
RP2040-asm-extensions uni.f | RP2040 ass. extensions | noForth assembler ext.f |
Contributions
en/pfw/assemblers_rp2040-assembler.txt · Last modified: 2023-10-02 17:04 by willem