AAC_SRCV_MAILBOX
AAC_MEM0_SETREG4(sc, AAC_SRCV_MAILBOX, command);
AAC_MEM0_SETREG4(sc, AAC_SRCV_MAILBOX + 4, arg0);
AAC_MEM0_SETREG4(sc, AAC_SRCV_MAILBOX + 8, arg1);
AAC_MEM0_SETREG4(sc, AAC_SRCV_MAILBOX + 12, arg2);
AAC_MEM0_SETREG4(sc, AAC_SRCV_MAILBOX + 16, arg3);
return(AAC_MEM0_GETREG4(sc, AAC_SRCV_MAILBOX + (mb * 4)));