Programming Copper

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.

The 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.

• VP vertical position 0,…,255: since there are 262 beam positions in NTSC, 0,…,6 refer to the last 7 lines before vertical blanking
• HP horizontal position 0,…,112: 4 or 8 lines are aggregated
• bfd blitter finished disable bit: if 0 the Copper will wait until Blitter has set blitter finished flag
• VE vertical compare enable: for each 0, the comparison with the according bit in VP is always true
• HE horizontal 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

(see WAIT for reference)