Intel PXA255 - Manual (Page 151)

Intel® PXA255 Processor Developer’s Manual 5-1
DMA Controller
5
This chapter describes the on-chip DMA controller (DMAC) for the PXA255 processor. The
DMAC transfers data to and from main memory in response to requests generated by internal and
external peripherals. The peripherals do not directly supply addresses and commands to the
memory system. The DMAC has 16 DMA channels, 0 through 15, and every DMA request from
the peripheral generates at least one memory bus cycle.
5.1 DMA Description
The DMAC supports only flow-through transfers.
Flow-through data passes through the DMAC before the data is latched by the destination in its
buffers/memory. This DMAC can perform memory-to-memory moves with flow-through transfers.
Figure 5-1 provides an overview of the DMAC. Table 5-1 provides a list of the DMAC signals and
descriptions.
Figure 5-1. DMAC Block Diagram
DDADR0
DSADR0
DTADR0
DCMD0
Channel 0
Channel 15
16 DMA Channels
DRCMR0
Control Registers
System Bus (internal)
Peripheral Bus
DREQ[1:0]
PREQ[37:0]
DMA_IRQ
DMA Controller
DINT
DCSR0
(external)
(internal)
(internal)
(internal)
Memory Controller