Changes

In the [[KC compact ]] system, the functions of the Gate-Array are "emulated" in [[TTL logic]] and by the [[Zilog Z8536 CIO]].

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>7 0 Gate Array function "Pen Selection"6 05 x not used4 0 Select pen3 x Pen Number2 x1 x0 x  ==== Colour selection<br>==== Once the pen has been selected the colour can then be changed. Bits 4 to 0 specify the hardware colour number from the hardware colour palette.

Summary<br> Bit Value Function <br> 7 0 Gate Array function "Colour Selection" <br>6 1 <br>5 x not used <br>4 x Colour number <br>3 x <br>2 x <br>1 x <br>0 x

==== Screen mode selection====

<br>{|{{Prettytable|width: 700px; font-size: 2em;}}|''Bit 1''||''Bit 0''||''Screen mode'' |-|0||0||Mode 0, 160x200 resolution, 16 colours|-|0||1||Mode 1, 320x200 resolution, 4 colours|-|1||0||Mode 2, 640x200 resolution, 2 colours|-|1||1||Mode 3, 160x200 resolution, 4 colours (note 1)|-|} This mode is not official. From the combinations possible, we can see that 4 modes can be defined, although the Amstrad only has 3. Mode 3 is similar to mode 0, because it has the same resolution, but it is limited to only 4 colours. <br> Mode changing is synchronised with HSYNC. If the mode is changed, it will take effect from the next HSYNC. <br> ==== Rom configuration selection<br>==== Bit 2 is used to enable or disable the lower rom area. The lower rom area occupies memory addressess &amp;0000-&amp;3fff and is used to access the operating system rom. When the lower rom area is is enabled, reading from &amp;0000-&amp;3FFF will return data in the rom. When a value is written to &amp;0000-&amp;3FFF, it will be written to the ram underneath the rom. When it is disabled, data read from &amp;0000-&amp;3FFF will return the data in the ram.