# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1598214374 -7200
# Node ID 0ddf105800424bdc6cf7df23c0f4a5aa5ad65dcd
# Parent  2636c1a88ee2e8215b38848296aa4f0f18f59a6e
Expanded mode property relationship descriptions; introduced tables.

diff -r 2636c1a88ee2 -r 0ddf10580042 ULA.txt
--- a/ULA.txt	Sun Aug 23 17:26:06 2020 +0200
+++ b/ULA.txt	Sun Aug 23 22:26:14 2020 +0200
@@ -733,19 +733,31 @@
 
 From these, the following properties emerge:
 
- * The number of bytes per character row
- * The size of the entire display in bytes
- * Pixel frequency or horizontal resolution
- * The number of character rows
+  Property                        Influences
+  --------                        ----------
+  Character row size (bytes)      Retrieval rate
+
+  Number of character rows        Text mode setting
+
+  Display size (bytes)            Retrieval rate (character row size)
+                                  Text mode setting (number of rows)
+
+  Pixel frequency                 Retrieval rate
+  Horizontal resolution (pixels)  Colour depth
 
 One can imagine a register bitfield arrangement as follows:
 
- * Pixel depth: log2(depth)
-   (00 - 1 bit per pixel, 01 - 2 bits per pixel, 10 - 4 bits per pixel)
- * Retrieval rate: 2 - fetches per cycle pair
-   (0 - twice, 1 - once)
- * Text mode enable
-   (0 - disable, 1 - enable)
+  Field             Values                  Formula
+  -----             ------                  -------
+  Pixel depth       00: 1 bit per pixel     log2(depth)
+                    01: 2 bits per pixel
+                    10: 4 bits per pixel
+
+  Retrieval rate     0: twice               2 - fetches per cycle pair
+                     1: once
+
+  Text mode enable   0: disable/off         text mode enabled
+                     1: enable/on
 
 This arrangement would require four bits. However, one bit in &FE07 is
 seemingly inactive and might possibly be reallocated.