На тази фирма компилатора (както и симулатора) са платени. Аз ти го посочих понеже спомена симулатор. И е перфектен за въвеждане в архитектурата.
В първия пост не става видно че под "компилатор" имаш в предвид асемблерски ...
Средата за развитие на Microchip е безплатна (в частта си за асемблер) и се казва MPLAB
Но тази информация си я има на сайта им - предположих, че ако някой има интерес първо проверява официалния сайт, а после пита 
 Free components of MPLAB IDE:
Free components of MPLAB IDE:
Programmer’s text editor 
MPLAB SIM, high speed software simulator for PICmicro and dsPIC MCUs with peripheral simulation, complex stimulus injection and register logging 
Full featured debugger 
Graphical project manager 
Visual Device Initializer (VDI) 
Version control support for MS Source Safe, CVS, PVCS, Subversion 
Application Maestro™ configurable firmware module library 
MPASM™ macro assembler with MPLINK™ linker and MPLIB™ librarian 
MPLAB ASM30 assembler, MPLAB LINK30 and Utilities for PIC24 and dsPIC devices 
PROCMD command line programmer for MPLAB PM3 and PRO MATE® II 
Visual PROCMD for simplified GUI control of MPLAB PM3 and PRO MATE® II 
Application Maestro 
dsPIC Motor Control plug-in 
CMX Scheduler viewer plug-in 
CMX Tiny+ RTOS viewer plug-in
These MPLAB components and add-ons can be purchased separately:
MPLAB® C18 Compiler (free student edition available for download) 
MPLAB C30 Compiler (free student edition available for download) 
MPLAB ICD 2 In-Circuit Debugger and engineering programmer for selected Flash devices 
MPLAB ICE 2000 In-Circuit Emulator 
MPLAB ICE 4000 In-Circuit Emulator 
PICSTART Plus Development Programmer 
MPLAB PM3 Device Programmer 
Third Party tools, including HI-TECH, IAR, Byte Craft, B. Knudsen, CCS and microEngineering Labs 
A host of low cost demonstration and evaluation kits 
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en019469&part=SW007002