ChSotiriou / riscv-from-scratch

RISCV From Scratch

Following the lessons from BrunoLevy/learn-fpga

SOC Datasheet

Memory Map

Address Start	Address End	Description
0x00000000	0x00000400	RAM
0x00400004	0x00400007	GPIO (Outputs)

RISCV Instruction Set

RISCV Instruction Set Reference Manual

• RISCV uses a modular instruction set

RV32I - 32bit Base Integer Instruction Set

• 32x 32bit Registers - x0 to x31
  • x0 is the "zero register", hardwired to all zero
• Registers have a specific function in the ABI

Register	ABI Name	Description
x0	zero	Hard-Wired Zero
x1	ra	Return Address
x2	sp	Stack Pointer
x3	gp	Global Pointer
x4	tp	Thread Pointer
x5	t0	Temporary Register
x6	t1	Temporary Register
x7	t2	Temporary Register
x8	s0	Saved Register / Frame Pointer
x9	s1	Saved Register
x10	a0	Function Argument 0 / Return Value
x11	a1	Function Argument 1
x12	a2	Function Argument 2
x13	a3	Function Argument 3
x14	a4	Function Argument 4
x15	a5	Function Argument 5
x16	a6	Function Argument 6
x17	a7	Function Argument 7
x18	s2	Saved Register
x19	s3	Saved Register
x20	s4	Saved Register
x21	s5	Saved Register
x22	s6	Saved Register
x23	s7	Saved Register
x24	s8	Saved Register
x25	s9	Saved Register
x26	s10	Saved Register
x27	s11	Saved Register
x28	t3	Temporary Register
x29	t4	Temporary Register
x30	t5	Temporary Register
x31	t6	Temporary Register