Writing to one of the two registers
COPJMPn (n = 1,2) causes a strobe and forces the copper to start operation and load the copper list beginning at the address in
COPLCn. The commands in the copper list, that is the sequence of copper commands in chipmem, is executed one by one. The Copper is restarted at each vertical blanking, forcing it to reload the command
COPLCn points to.
Copper can call the CPU's attention by filing an interrupt request in
INTREQ. It can also move data into
COPLCn to form a loop. To stop, Copper can either wait for the impossible, or turn its own access to DMA off.
CDANG bit in
COPCON permits access to 1 the register address space between $40 and $7, including Blitter's registers.
Copper lists can consist of the following instructions:
waits until video beam counter is greater or equal the argument During WAIT the memory bus will not be accessed, freeing it for different tasks. The bus is accessed at uneven memory cycles.
VPvertical position 0,…,255: since there are 262 beam positions in NTSC, 0,…,6 refer to the last 7 lines before vertical blanking
HPhorizontal position 0,…,112: 4 or 8 lines are aggregated
bfdblitter finished disable bit: if 0 the Copper will wait until Blitter has set blitter finished flag
VEvertical compare enable: for each 0, the comparison with the according bit in VP is always true
HEhorizontal compare enable: for each 0, the comparison with the according bit in HP is always true
moves data word into secified data register
DA: the destination register's address
data: one word of data to be written to the destination register
skip next instruction if video beam counter is greater or equal the argument
WAIT for reference)