Commodore Amiga A2000 - USING THE COPPER REGISTERS

USING THE COPPER REGISTERS
There are several machine registers and strobe addresses dedicated to the Copper:
o Location registers
o Jump address strobes
o Control register
LOCATION REGISTERS
The Copper has two sets of location registers:
COP1LCH High 3 bits of first Copper list address.
COP1LCL Low 16 bits of first Copper list address.
COP2LCH High 3 bits of second Copper list address.
COP2LCL Low 16 bits of second Copper list address.
In accessing the hardware directly, you often have to write to a pair of registers that
contains the address of some data. The register with the lower address always has a
name ending in "H" and contains the most significant data, or high 3 bits of the address.
The register with the higher address has a name ending in "L" and contains the least
significant data, or low 15 bits of the address. Therefore, you write the 18-bit address by
moving one long word to the register whose name ends in "H." This is because when you
write long words with the 68000, the most significant word goes in the lower addressed
word.
In the case of the Copper location registers, you write the address to COP1LCH. In the
following text, for simplicity, these addresses are referred to as COP1LC or COP2LC.
The Copper location registers contain the two indirect jump addresses used by the
Copper. The Copper fetches its instructions by using its program counter and increments
the program counter after each fetch. When a jump address strobe is written, the
corresponding location register is loaded into the Copper program counter. This causes the
Copper to jump to a new location, from which its next instruction will be fetched.
Instruction fetch continues sequentially until the Copper is interrupted by another jump
address strobe.
- 20 Coprocessor Hardware -