From 0802df22f0a34567ee2d438c1d7e6867f5b8c3d8 Mon Sep 17 00:00:00 2001
From: "Darryl L. Miles" <darryl.miles@darrylmiles.org>
Date: Fri, 6 Oct 2023 18:12:42 +0100
Subject: [PATCH] Simulation/signal: Load and Store of Memory in Simulation

---
 source/SpinalHDL/Sequential logic/memory.rst |  3 +++
 source/SpinalHDL/Simulation/signal.rst       | 28 ++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/source/SpinalHDL/Sequential logic/memory.rst b/source/SpinalHDL/Sequential logic/memory.rst
index f597e4ecab8..fe5b6a31240 100644
--- a/source/SpinalHDL/Sequential logic/memory.rst	
+++ b/source/SpinalHDL/Sequential logic/memory.rst	
@@ -28,6 +28,9 @@ The following table shows how to instantiate a memory:
    Write mask width is flexible, and subdivide the memory word in as many slices of equal width as the width of the mask. 
    For instance if you have a 32 bits memory word and provide a 4 bits mask then it will be a byte mask. If you provide a as many mask bits than you have word bits, then it is a bit mask.
 
+.. note::
+   Manipulation of ``Mem`` is possible in simulation, see section :ref:`Load and Store of Memory in Simulation <simulation_of_memory>`.
+
 The following table show how to add access ports on a memory :
 
 .. list-table::
diff --git a/source/SpinalHDL/Simulation/signal.rst b/source/SpinalHDL/Simulation/signal.rst
index cb5e359451f..ecd85e92ab9 100644
--- a/source/SpinalHDL/Simulation/signal.rst
+++ b/source/SpinalHDL/Simulation/signal.rst
@@ -44,6 +44,34 @@ Each interface signal of the toplevel can be read and written from Scala:
    dut.io.a #= BigInt("0123456789ABCDEF", 16)
    println(dut.io.b.toInt)
 
+
+.. _simulation_of_memory:
+
+Load and Store of Memory in Simulation
+--------------------------------------
+
+It is possible to modify the contents of ``Mem`` hardware interface
+components in simulation.  The `data` argument should be a word-width
+value with the `address` being the word-address within.
+
+There is no API to convert address and/or individual data bits into
+units other than the natural word size.
+
+There is no API to mark any memory location with simulation `X` (undefined)
+state.
+
+.. list-table::
+   :header-rows: 1
+   :widths: 3 5
+
+   * - Syntax
+     - Description
+   * - ``Mem.getBigInt(address: Long): BigInt``
+     - Read a word from simulator at the word-address.
+   * - ``Mem.setBigInt(address: Long, data: BigInt)``
+     - Write a word to simulator at the word-address.
+
+
 Accessing signals inside the component's hierarchy
 --------------------------------------------------