Copper Lists

You should now understand that AMOS Professional actually holds two separate copper lists in memory, and the principle is very similar to the logical and physical screens of the DOUBLE BUFFER system.

The logical copper list is the list being created from AMOS Professional Basic, and it is completely invisible. The physical list holds the copper instructions that are generating the current TV display. It cannot be accessed from AMOS Professional at all, as this would corrupt the display completely. As a default, these copper lists are limited to 12k in length, which is the equivalent to approximately six thousand instructions. This limit may be increased using an option from the Interpreter set-up dialogue box.

Copper lists can be defined in one of three ways:

The first method is to enter the copper list using a combination of the COP MOVE and COP WAIT instructions, from AMOS Professional Basic.

The second way is to find the address of the logical copper list, using COP LOGIC. This can then be manipulated directly using DEEK and DOKE, allowing minor modifications to be made to the existing screen without having to generate a completely new copper list at all. This is perfect for the creation of rainbow effects.

The third alternative is for assembly language buffs. Copper lists can be generated using machine code, and as before, the current address is available via the COP LOGIC function. Note that this address will change during the course of a program, and it must be entered every time the machine code routine is called.

Recommended Procedures
If you want to create copper lists from beginning to end, you must take personal control over the hardware Sprites, the display positioning, the location of screens, and their sizes. You must then ensure that the resulting screens have the correct amount of memory, before loading the appropriate registers with the addresses of the required bitmaps. This can be achieved with the LOGBASE function.

Additionally, if you intend to use DOUBLE BUFFER, a separate copper list must be produced for both the logical and physical screens. Here is the procedure:

• Define the copper list for the first screen.
• Switch copper lists using the COP SWAP command.
• Swap between the logical and physical screens with SCREEN SWAP.
• Define a copper list for the second screen.

Providing that all is well, you may access your screens using -all of the normal AMOS Professional drawing commands, including SCREEN COPY, DRAW, PRINT and PLOT. As well as this, there should be no problems using Blitter Objects.