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CLASS #5: Indirect with or without auto-inc and read/write channel indirect

Load/Store to register:

    101 rrr 0ip xxx        p=0 => rrr <-- [xxx] ; Load indirect   { ldx r, x }
                           p=1 => rrr --> [xxx] ; Store indirect  { stx r, x }
                           i=1    => Increment xxx after transfer { ldy r, x }{ sty r, x }

Read/Write to selected channel:

    101 000 10p xxx        p=0 => [xxx] <-- Channel Data path ; read data indirect  { ldch x }
                           p=1 => [xxx] --> Channel Data path ; write data indirect { stch x }
                          
    101 000 11p xxx        p=0 => [xxx] <-- Channel Control reg ; read ctl indirect  { ldct x }
                           p=1 => [xxx] --> Channel Control reg ; write ctl indirect { stct x }

These last four instructions provide the only way to access peripherals by software. Transfer is always indirect between Memory and the selected channel, using any of the suitable register as a pointer.