Add VIA-CUDA description.

devices/macio.h

@@ -10,7 +10,7 @@
     - Macintosh Enhanced SCSI Hardware (MESH)
 
     In the 68k Macintosh era, all this hardware was implemented using several
-    custom chips. In PCI-compatible Power Macintosh, the above devices are part
+    custom chips. In a PCI-compatible Power Macintosh, the above devices are part
     of the MIO chip itself. MIO's functional blocks implementing virtual devices
     are called "cells", i.e. "VIA cell", "SWIM cell" etc.
 

devices/mpc106.h

@@ -13,7 +13,7 @@
     It's the central device in the Gossamer architecture.
     Manual: https://www.nxp.com/docs/en/reference-manual/MPC106UM.pdf
 
-    This code emulate as much functionality as needed to run PowerMac Beige G3.
+    This code emulates as much functionality as needed to run PowerMac Beige G3.
     This implies that
     - we only support address map B
     - our virtual device reports revision 4.0 as expected by machine firmware

devices/viacuda.cpp

@@ -5,7 +5,6 @@
 //if you want to distribute this.
 //(divingkatae#1017 on Discord)
 
-//Functionality for the VIA CUDA
 
 #include <iostream>
 #include <cinttypes>

devices/viacuda.h

@@ -5,6 +5,29 @@
 //if you want to distribute this.
 //(divingkatae#1017 on Discord)
 
+/** VIA-CUDA combo device emulation.
+
+    Author: Max Poliakovski 2019
+
+    Versatile interface adapter (VIA) is an old I/O controller that can be found
+    in nearly every Macintosh computer. In the 68k era, VIA was used to control
+    various peripherial devices. In a Power Macintosh, its function is limited
+    to the I/O interface for the Cuda MCU. I therefore decided to put VIA
+    emulation code here.
+
+    Cuda MCU is a multipurpose IC built around a custom version of the Motorola
+    MC68HC05 microcontroller. It provides several functions including:
+    - Apple Desktop Bus (ADB) master
+    - I2C bus master
+    - Realtime clock (RTC)
+    - parameter RAM
+    - power management
+
+    MC68HC05 doesn't provide any dedicated hardware for serial communication
+    protocols. All signals required for ADB and I2C will be generated by Cuda
+    firmware using bit banging (https://en.wikipedia.org/wiki/Bit_banging).
+*/
+
 #ifndef VIACUDA_H
 #define VIACUDA_H