MAC7200 datasheet(284/976 Pages) FREESCALE

284 / 976 page

The SPP DMA Controller Module (SPP_DMA2)

MAC7200 Microcontroller Family Reference Manual, Rev. 2

206

Freescale Semiconductor

/* generate the next-state destination address */

/* sum the current daddr with the signed destination offset */

ns_addr = dma_engine.daddr + (int) dma_engine.doff;

/* if enabled, apply the power-of-2 modulo to the next-state dest addr */

if (dma_engine.dmod != 0)

address_select = (1 << dma_engine.dmod) - 1;

else

address_select = 0xffff_ffff;

dma_engine.daddr = ns_addr

address_select

| dma_engine.daddr & ~address_select;

}

/* check for a higher priority channel to service if: */

/* 1) preemption is enabled */

/* 2) in fixed arbitration mode */

/* 3) a higher priority channel is requesting service */

/* 4) not already servicing a preempting channel */

if ((DCHPRIn.ecp = 1)

fixed_arbitration_mode

higher_pri_request & ~current_channel_is_preempt)

service_preempt_channel;

/* the bandwidth control field determines when the next read/write occurs */

if (dma_engine.bwc > 1)

stall_dma_engine (1 << dma_engine.bwc);

/* decrement the minor loop byte count */

dma_engine.nbytes = dma_engine.nbytes - xfr_size;

}while (dma_engine.nbytes > 0) /* end of minor inner loop */

dma_engine.citer--;

/* decrement major loop iteration count */

/* if the major loop is not yet exhausted, update certain TCD values in the RAM */

if (dma_engine.citer != 0) {

write_to_local_memory [channel].saddr = dma_engine.saddr;

write_to_local_memory [channel].daddr = dma_engine.daddr;

write_to_local_memory [channel].citer = dma_engine.citer;

/* if minor loop linking is enabled, make the channel link */

if (dma_engine.citer.e_link)

TCD[citer.linkch].start = 1;

/* specified channel service req */

/* check for interrupt assertion if half of the major iterations are done */

if (dma_engine.int_half && (dma_engine.citer == (dma_engine.biter >> 1)))

generate_interrupt (channel);

dma_engine.active = 0;

/* clear the channel busy flag */

}

else { /* major loop is complete, dma_engine.citer == 0 */

/* since the major loop is complete, perform the final address adjustments */

/* sum the current {src,dst} addresses with “last” adjustment */

write_to_local_memory [channel].saddr = dma_engine.saddr + dma_engine.slast;

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