RainingComputers / SRP16

SRP16 is free and open ISA for 16-bit CPUs and Microcontrollers.

SRP16

SRP16 is free and open ISA for 16-bit CPUs and Microcontrollers.

Project Status

Specification

• SRP16 ISA Specifaction [.pdf]
• SRP16 Assembler Guide [.pdf]
• SRP16 ISA Simulator Manual [.pdf]
• .dhex File Specification [.pdf]

Roadmap

• ISA Specification
• Reference Implementation in Icarus Verilog
• Reference Implementation in Lattice iCEstick
• Assembler
• ISA Simulator
• I/O, Interrupts and Timers

ISA Quick Reference

Registers:

• General Purpose Registers R0-R15 (Accessible by Load-Store Instructions)
• General Purpose Registers R16-R31 (Not Accessible by Load-Store Instructions)
• Accumulator Register (R60)
• Memory Pointer Register or MPTR (R61)
• Stack Pointer or SP (R62)
• Program Counter or PC (R63)
• POP, PUSH, INC, DEC instructions can only access General Purpose Registers R0-R31

Instructions:

Instruction	Operation
LDR Rx, 8-bit-signed-immediate	Rx ⟵ immediate
LDRU Rx, 8-bit-unsigned-immediate	Rx[15:8] ⟵ immediate
LD@MPTR Rx, 8-bit-signed-offset	Rx ⟵ memory[MPTR] MPTR ⟵ MPTR+offset
ST@MPTR Rx, 8-bit-signed-offset	memory[MPTR] ⟵ Rx MPTR ⟵ MPTR+offset
LDB@MPTR Rx, 8-bit-signed-offset	Rx[7:0] ⟵ memory[MPTR] MPTR ⟵ MPTR+offset
STB@MPTR Rx, 8-bit-signed-offset	memory[MPTR] ⟵ Rx[7:0] MPTR ⟵ MPTR+offset
LDA 12-bit-signed-immediate	A ⟵ immediate
LDAU 6-bit-unsigned-immediate	A[15:12] ⟵ immediate[3:0]
LDMPTR 12-bit-unsigned-immediate	MPTR ⟵ immediate
LDMPTRU 12-bit-signed-immediate	MPTR[15:12] ⟵ immediate[3:0]
MOV Rx, Ry	Rx ⟵ Ry
MOV Rx, PC	Rx ⟵ PC+4
JMP Ry or MOV PC, Ry	PC ⟵ Ry
SJMP 12-bit-signed-offset	PC ⟵ PC+offset
SJMPF 12-bit-signed-offset	if(flag): PC ⟵ PC+offset
NOTF	flag ⟵ !flag
POP Rx	Rx ⟵ memory[SP] SP ⟵ SP+1
PUSH Rx	SP ⟵ SP-1 memory[SP] ⟵ Rx
INC Rx	Rx ⟵ Rx+1
DEC Rx	Rx ⟵ Rx-1
ADDI 8-bit-signed-immediate	A ⟵ A+immediate
ADCI 8-bit-signed-immediate	A ⟵ A+immediate+carry
SBBI 8-bit-signed-immediate	A ⟵ A-immediate-carry
ANDI 8-bit-signed-immediate	A ⟵ A&immediate
ORI 8-bit-signed-immediate	A ⟵ A
XORI 8-bit-signed-immediate	A ⟵ A^immediate
SLAI 6-bit-unsigned-immediate	A ⟵ A<<<immediate
SRAI 6-bit-unsigned-immediate	A ⟵ A>>>immediate
SLLI 6-bit-unsigned-immediate	A ⟵ A<<immediate
SRLI 6-bit-unsigned-immediate	A ⟵ A>>immediate
ADD Rx	A ⟵ A+Rx
SUB Rx	A ⟵ A-Rx
ADC Rx	A ⟵ A+Rx+carry
SBB Rx	A ⟵ A-Rx-carry
AND Rx	A ⟵ A&Rx
OR Rx	A ⟵ A
XOR Rx	A ⟵ A^Rx
SLA Rx	A ⟵ A<<<Rx
SRA Rx	A ⟵ A>>>Rx
SLL Rx	A ⟵ A<<Rx
SRL Rx	A ⟵ A>>Rx
CLI 8-bit-signed-immediate	if(A<immediate): flag ⟵ 1 else: flag ⟵ 0
CGI 8-bit-signed-immediate	if(A>immediate): flag ⟵ 1 else: flag ⟵ 0
CEI 8-bit-signed-immediate	if(A==immediate): flag ⟵ 1 else: flag ⟵ 0
CL Rx	if(A<Rx): flag ⟵ 1 else: flag ⟵ 0
CG Rx	if(A>Rx): flag ⟵ 1 else: flag ⟵ 0
CE Rx	if(A==Rx): flag ⟵ 1 else: flag ⟵ 0

Installing toolchain

• Clone repo, cd into it

git clone https://github.com/RainingComputers/SRP16.git
cd SRP16

• Install readline library

sudo apt-get install libreadline-dev

• Compile and build executable,

make build

• Install, requires root privilege

sudo make install

Getting started

Let's write a simple program to generate fibonacci numbers, and save it as test.asm

	lda 1					
	ldr r0, 0		;Load initial values		
	ldr r1, 1				
loop:						
	add r0					
	mov r0, r1			
	mov r1, a		;Add to accumulator		
	sjmp loop		;Loop

Now to assemble the program,

srp16asm test.asm -s test.dhex

Now, to start the simulator,

srp16sim test.dhex

You will see a prompt,

(pc@0x0000) █  

Let's set a break point at end of the loop,

(pc@0x0000) bp "test.asm" 8

Now use run command to run it, and a to view contents of the accumulator,

(pc@0x0000) run
(pc@0x000c) a
a = 0x0001
(pc@0x000c) run
(pc@0x000c) a
a = 0x0002
(pc@0x000c) run
(pc@0x000c) a
a = 0x0003
(pc@0x000c) run
(pc@0x000c) a
a = 0x0005

License

• MIT License. See: https://github.com/RainingComputers/SRP16/blob/master/LICENSE.md