docs

docs/source/emulator.rst

@@ -3,15 +3,26 @@
 Emulator
 ========
 
-The **emulator** runs the program and displays the runtime status
-of the program counter, registers, decoded instructions, etc.
+The Q1 Emulator architecture is shown below. Operationally it consists of
+two paths, one for initialisation (blue arrows going up) and one for the runtime
+emulation (yellow arros going down). The Q1 Emulator makes use of a **z80
+emulator** which in turn interfaces to **memory** and **IO**. Memory is loaded
+with **programs** by a **loader** and IO devices are initialised: **display buffer**
+is cleared and **disk** is populated with a **filesystem**. These abstractions
+are described in the **Python Modules** section.
+
+On the initialisation is done the emulator enters a repeated series of single
+instruction **steps**.
+
 
 .. figure:: images/emuarch.png
   :width: 800
   :align: center
 
   Q1 Emulator Architecture
 
+  The **emulator** runs the program and displays the runtime status
+  of the program counter, registers, decoded instructions, etc.
 
 The emulator can be run with disassembly: