Changes
CRTC
,|}
'''NOTE: '''
1. The function of these I/O ports is dependant on the CRTC type
{|{{Prettytable|width: 700px; font-size: 2em;}}
|''Memory Address Signal''||''Signal source''||''Signal name''
|-
|A15||6845||MA12
|-
|A14||6845||MA11
|}
== DISPTMG ==
DISPTMG signal defines the border. When DISPTMG is "1" the border colour is output to the display.
== HSYNC and VSYNC ==
HSYNC and VSYNC from the CRTC are passed into the Gate-Array. The Gate-Array modifies the signals and then mixes these to form the Composite-Sync which is output to the display
The 6845 Design
Registers
== The Internal registers of the 6845 are == {|{{Prettytable|width: 700px; font-size: 2em;}}|''Register Index ''||''Register Name ''|-|0 ||Horizontal Total |-|1 ||Horizontal Displayed |-|2 ||Horizontal Sync Position |-|3 ||Horizontal and Vertical Sync Widths |-|4 ||Vertical Total |-|5 ||Vertical Total Adjust |-|6 ||Vertical Displayed |-|7 ||Vertical Sync position |-|8 ||Interlace and Skew |-|9 ||Maximum Raster Address |-|10 ||Cursor Start Raster |-|11 ||Cursor End Raster |-|12 ||Display Start Address (High) |-|13 ||Display Start Address (Low) |-|14 ||Cursor Address (High) |-|15 ||Cursor Address (High) |-|16 ||Light Pen Address (High) |-|17 Light Pen Address (High) |-|}
== CRTC Differences ==
In this section I will attempt to identify all the differences between each CRTC.
