The function to be performed is selected by writing data to the Gate-Array, bit 7 and 6 of the data define the function selected (see table below). It is not possible to read from the Gate-Array.
{|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit 7 ''||''Bit 6 ''||''Function'' |-|0 ||0 ||Select pen|-|0 ||1 ||Select colour for selected pen|-|1 1 ||0||Select screen mode, rom configuration and interrupt control|-|1 ||1 ||Ram Memory Management (note 1)|-|}
=== 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. <br> ==== Pen selection<br>==== When bit 7 and bit 6 are set to "0", the remaining bits determine which pen is to have its colour changed. When bit 4 is set to "0", bits 3 to 0 define which pen is to be selected. When bit 4 is set to "1", the value contained in bits 3-0 is ignored and the border is selected.
The pen remains selected until another is chosen.
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<br> Bit Value Function <br>7 0 Gate Array function "Pen Selection" <br>6 0 <br>5 x not used <br>4 1 Select border <br>3 x ignored <br>2 x ignored <br>1 x ignored <br>0 x ignored
Bit Value Function <br>7 0 Gate Array function "Pen Selection" <br>6 0 <br>5 x not used <br>4 0 Select pen <br>3 x Pen Number <br>2 x <br>1 x <br>0 x
<br>Hardware colour palette:
Colour Number Colour Name <br> {|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit 7''||''Bit 6''||''Function'' |-|0 ||White <br>|-|1 ||White (note 1) <br>|-|2 ||Sea Green <br>|-|3 ||Pastel Yellow <br>|-|4 ||Blue <br>|-|5 ||Purple <br>|-|6 ||Cyan <br>|-|7 ||Pink <br>|-|8 ||Purple (note 1) <br>|-|9 ||Pastel Yellow (note 1) <br>|-|10 ||Bright Yellow <br>|-|11 ||Bright White <br>|-|12 ||Bright Red <br>|-|13 ||Bright Magenta <br>|-|14 ||Orange <br>|-|15 ||Pastel Magenta <br>|-|16 ||Blue (note 1) <br>|-|17 ||Sea Green (note 1) <br>|-|18 ||Bright Green <br>|-|19 ||Bright Cyan <br>|-|20 ||Black <br>|-|21 ||Bright Blue <br>|-|22 ||Green <br>|-|23 ||Sky Blue <br>|-|24 ||Magenta <br>|-|25 ||Pastel Green <br>|-|26 ||Lime <br>|-|27 ||Pastel Cyan <br>|-|28 ||Red <br>|-|29 ||Mauve <br>|-|30 ||Yellow <br>|-|31 ||Pastel Blue|-|}
== Notes ==