Copper Control High Byte

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Number $62
Readable Yes
Writable Yes
Short Description Holds high byte of Copper control flags.
Bit Function
7-6 Control mode
5-3 Reserved, must be 0
2-0 High three bits of Copper list index (value 0-2047)

When "Control mode" bits are identical with previously set ones, they are ignored - allowing for index change without restarting currently running Copper program.

Copper has internally 10 bit "program counter" register (CPC), going through 0-1023 values, executing Copper instruction from the list at memory position (CPC*2). This will cause the Copper program to loop automatically. To "halt" program (avoiding possible loop), use WAIT instruction with non-existent horizontal line, like "WAIT 63,511 = 0xFF, 0xFF".

To change control mode, the new value must differ from previous, the possible control modes are:

Bits 7-6 Control mode
%00 STOP Copper (CPC is kept at current value)
%01 Reset CPC to 0 and START Copper
%10 START Copper (does resume at current CPC)
%11 Reset CPC to 0 and START Copper, reset CPC at each video frame at (0,0) (top left pixel of PAPER area)

NEW in core 3.0:

The register is now also readable.