From 59db9335448b568ccff9964aec0626a23387597f Mon Sep 17 00:00:00 2001
From: Warrick Lo <wlo@warricklo.net>
Date: Wed, 27 May 2026 20:40:30 -0700
Subject: Update README and WaveDrom diagrams [skip ci]

Signed-off-by: Warrick Lo <wlo@warricklo.net>
---
 README.adoc | 248 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 248 insertions(+)
 create mode 100644 README.adoc

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+Montreal
+========
+:revnumber: 0.1.0-draft
+
+A RISC-V RV32E processor designed for TinyTapeout.
+
+RV32E
+-----
+
+https://docs.riscv.org/reference/isa/unpriv/unpriv-index.html[ISA Reference]
+
+Reduces number of integer registers to 16 general-purpose registers
+(x0-x15). Upper 16 registers consume around one quarter of the total
+area of the core excluding memories, thus their removal saves around 25%
+core area with a corresponding core power reduction.
+
+Each register is 32 bits wide.
+
+[cols="1,2,4", options="header"]
+|===
+
+| Register
+| Description
+| Purpose
+
+| x0
+| dedicated zero
+| Source operand for value 0.
+
+| x1
+| return address
+| Written by JAL/JALR. Holds address to be returned to once a function returns.
+Must be saved to stack before calling another function.
+
+| x2
+| stack pointer
+| Always points to top of the stack in RAM. Decremented to allocate space,
+incremented to free it. CALLEE must restore it BEFORE returning.
+
+| x3
+| global pointer
+|
+
+| x4
+| thread pointer
+|
+
+| x5
+| alternate link reg
+| Second link register for nested JAL sequences. Caller must save
+if needed across a call.
+
+| x6
+| general scratch reg
+|
+
+| x7
+| general scratch reg
+|
+
+| x8
+| frame pointer
+|
+
+| x9
+| saved register
+|
+
+| x10
+| first function argument
+| Also used to return integer results from function.
+
+| x11
+| second function argument
+|
+
+| x12
+| third function argument
+|
+
+| x13
+| fourth function argument
+|
+
+| x14
+| fifth function argument
+|
+
+| x15
+| sixth function argument
+|
+
+| pc
+| program counter
+| Address of current instruction
+
+|===
+
+Instruction Set
+---------------
+
+.Relevant opcodes for the IP. `inst[1:0] = 11`.
+[cols="2*^1m,8*^2m", hrows=2]
+|===
+
+|
+|
+8+^| inst[4:2]
+
+|
+|
+| 000
+| 001
+| 010
+| 011
+| 100
+| 101
+| 110
+| 111
+
+1.4+.^| inst[6:5]
+| 00
+| LOAD
+|
+|
+| MISC-MEM
+| OP-IMM
+| AUIPC
+|
+|
+
+| 01
+| STORE
+|
+|
+|
+| OP
+| LUI
+|
+|
+
+| 10
+|
+|
+|
+|
+|
+|
+|
+|
+
+| 11
+| BRANCH
+| JALR
+|
+| JAL
+| SYSTEM
+|
+|
+|
+|===
+
+=== Immediate Types
+
+The labels `[7]`, `[20]`, and `[31]` represent the bits `inst[7]`, `inst[20]`, and `inst[31]`, respectively.
+
+image::docs/images/i-immediate.svg[width=100%]
+image::docs/images/s-immediate.svg[width=100%]
+image::docs/images/b-immediate.svg[width=100%]
+image::docs/images/u-immediate.svg[width=100%]
+image::docs/images/j-immediate.svg[width=100%]
+
+=== LUI
+
+image::docs/images/lui.svg[width=100%]
+
+=== AUIPC
+
+image::docs/images/auipc.svg[width=100%]
+
+=== OP-IMM
+
+image::docs/images/addi.svg[width=100%]
+image::docs/images/slti.svg[width=100%]
+image::docs/images/sltiu.svg[width=100%]
+image::docs/images/xori.svg[width=100%]
+image::docs/images/ori.svg[width=100%]
+image::docs/images/andi.svg[width=100%]
+image::docs/images/slli.svg[width=100%]
+image::docs/images/srli.svg[width=100%]
+image::docs/images/srai.svg[width=100%]
+
+=== OP
+
+image::docs/images/add.svg[width=100%]
+image::docs/images/sub.svg[width=100%]
+image::docs/images/slt.svg[width=100%]
+image::docs/images/sltu.svg[width=100%]
+image::docs/images/xor.svg[width=100%]
+image::docs/images/or.svg[width=100%]
+image::docs/images/and.svg[width=100%]
+image::docs/images/sll.svg[width=100%]
+image::docs/images/srl.svg[width=100%]
+image::docs/images/sra.svg[width=100%]
+image::docs/images/czero.eqz.svg[width=100%]
+image::docs/images/czero.nez.svg[width=100%]
+
+=== JAL
+
+image::docs/images/jal.svg[width=100%]
+
+=== JALR
+
+image::docs/images/jalr.svg[width=100%]
+
+=== BRANCH
+
+The labels `[11]` and `[12]` represent the bits `imm[11]` and `imm[12]` respectively.
+
+image::docs/images/beq.svg[width=100%]
+image::docs/images/bne.svg[width=100%]
+image::docs/images/blt.svg[width=100%]
+image::docs/images/bge.svg[width=100%]
+image::docs/images/bltu.svg[width=100%]
+image::docs/images/bgeu.svg[width=100%]
+
+=== LOAD
+
+image::docs/images/lb.svg[width=100%]
+image::docs/images/lh.svg[width=100%]
+image::docs/images/lw.svg[width=100%]
+image::docs/images/lbu.svg[width=100%]
+image::docs/images/lhu.svg[width=100%]
+
+=== STORE
+
+image::docs/images/sb.svg[width=100%]
+image::docs/images/sh.svg[width=100%]
+image::docs/images/sw.svg[width=100%]
+
+=== MISC-MEM
+
+image::docs/images/fence.svg[width=100%]
+
+=== SYSTEM
+
+image::docs/images/ecall.svg[width=100%]
+image::docs/images/ebreak.svg[width=100%]
-- 
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