ARMv2a VLSI Project

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Made by

Samy Attal
Kevin Lastra

Description

This project aims to design in VHDL the "user" execution mode of a processor implementing the ARMv2a instruction set, to synthesize, and to generate its IC layout.

Outils

• Compiler : GHDL
• Wave viewer : gtkwave
• Logic synthetiser, automatic place and route : Suite Alliance/Coriolis

Global architecture

The processor core has a four-stage pipeline: fetch, decode, exec and mem:

Simulation

We analyze and validate the processor core with an assembler (or C) program used by a testbench and an emulation of the instruction and data caches (written in C). Here is an example:

/*----------------------------------------------------------------
//           test add                                           //
----------------------------------------------------------------*/
	.text
	.globl	_start 
_start:               
	/* 0x00 Reset Interrupt vector address */
	b	startup
	
	/* 0x04 Undefined Instruction Interrupt vector address */
	b	_bad

startup:                        
	mov r0, #0                  
	adds r1, r0, r0             
	bne _bad                    
	movs r0, #0x80000000        
	bpl _bad                    
	subs r0, r0, #1             
	bmi _bad                    
	b _good                   
_bad : 
	nop                         
	nop
_good :
	nop
	nop
AdrStack:  .word 0x80000000

We visualize the execution of the instructions with gtkwave:

Design of the masks

The mask design of the chip below is not optimized (being pad limited), an optimization at the level of the pads is required.

The IC layout pad limited. In order to optimize the silicon area we can imagine adding other execution modes (FIR, IRQ, Supervisor...) as well as integrating the caches.