Changes
|}
===== Note =====
This function is not available in the Gate-Array, but is performed by a device at the same I/O port address location. In the CPC464,CPC664 and KC compact, this function is performed in a memory-expansion (e.g. Dk'Tronics 64K Ram Expansion), if this expansion is not present then the function is not available. In the CPC6128, this function is performed by a PAL located on the main PCB, or a memory-expansion. In the 464+ and 6128+ this function is performed by the ASIC or a memory expansion. Please read the document on Ram Management for more information.
Each mode has a fixed number of pens. Mode 0 has 16 pens, mode 1 has 4 pens and mode 2 has 2 pens.
===== Summary=====
{|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit ''||''Value ''||''Function '' |-|7||0||Gate Array function "Pen Selection"|-|6||0|||-|5||x||not used|-|4||1||Select border|-|3||x||ignored|-|2||x||ignored|-|1||x||ignored|-|0||x||ignored|-|}
{|{{Prettytable|width: 700px; font-size: 2em;}}
|''Bit''||''Value''||''Function''
|-
|7||0||Gate Array function "Pen Selection"
|-
|6||0||
|-
|5||x||not used
|-
|4||1||Select pen
|-
|3||x||Pen number
|-
|2||x||
|-
|1||x||
|-
|0||x||
|-
|}
==== Colour selection ====
Even though there is provision for 32 colours, only 27 are possible. The remaining colours are duplicates of those already in the colour palette.
===== Summary=====
{|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit ''||''Value ''||''Function'' |-|7 ||0 ||Gate Array function "Colour Selectionselection"|-|6 ||1 |||-|5 ||x ||not used|-|4 ||x ||Colour number x |-|3||x|||-|2 ||x|||-|1 ||x|||-|0 ||x|||-<br>Hardware colour palette:|}
{|{{Prettytable|width: 700px; font-size: 2em;}}
|''Bit 7Colour Number''||''Bit 6''||''FunctionColour Name''
|-
|0||White
|}
===== Notes =====
This is not an official colour
The function of bits 1 and 0 is to define the screen mode. The settings for bits 1 and 0 and the corresponding screen mode are given in the table below.
{|{{Prettytable|width: 700px; font-size: 2em;}}
Bit 4 controls the interrupt generation. It can be used to delay interrupts. See the document on interrupt generation for more information.
===== Summary<br>===== {|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit ''||''Value ''||''Function <br>'' |-|7 ||0 ||Gate Array function <br>|-|6 ||1 <br>|||-|5 ||x ||not used <br>|-|4 ||x ||Interrupt generation control <br>|-|3 ||x||*1 Upper rom area disable <br>*0 Upper rom area enable <br>|-|2 ||x||*1 Lower rom area disable <br>*0 Lower rom area enable <br>|-|1 ||x ||Mode selection <br>slection|-|0 ||x|||-|}
== Programming the Gate Array - Examples ==
</pre>
==== Pallette R,G,B definitions====
There are 27 colours which are generated from red, green and blue mixed in different quantities. There are 3 levels of red, 3 levels of green and 3 levels of blue, and these can be thought of as off/no colour, half-on/half-colour, and on/full-colour.
