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DMA Controller
Copyright © 12/13/06 Marvell
CONFIDENTIAL
Doc. No. MV-TBD-00 Rev. A
December 13, 2006
Document Classification: Proprietary Information
Page 293
Not approved by Document Control. For review only.
DMA Controller
11
This chapter describes the PXA300 processor or PXA310 processor on-board DMA controller (DMAC).
11.1
Overview
The processor contains a direct-memory access controller (DMAC) that transfers data to and from memory in
response to requests generated by peripheral devices or companion chips. The peripheral devices and companion
chips do not directly supply addresses and commands to the memory controller. Instead, the states required to
manage a data stream are maintained in 32 DMA channels, DMA[31:0], in the DMAC. Every DMA request
from a peripheral device generates a memory-bus transaction. The processor can access the peripheral bus
through the bridge portion the DMA thus bypassing the system DMA. Hence, this document refers DMA as
DMA Bridge.
The DMAC supports flowthrough transfers only.
provides an overview of the DMAC.
11.2
Features
The DMAC provides the following features:
•
Supports memory-to-memory, peripheral-to-memory, and memory-to-peripheral transfers in flowthrough
mode.
•
Supports flowthrough mode for transfers between flash and DDR SDRAM.
•
Supports one external companion chip related transfer in flowthrough mode only. The external device might
also be an external peripheral, instead of a companion chip. Supports 32 channels, 92 peripheral-device
requests and one external device request, with the capability of pre-programming any request to any
channel.
•
Employs a priority mechanism to process active channels (four channels with outstanding DMA requests, at
any given time).
•
Allows each of the 32 channels to operate for descriptor-fetch or no-descriptor-fetch transfers (see
Section 11.3.2, “DMA Descriptors” on page 11-297
•
Supports special descriptor modes (descriptor comparison and descriptor branching).
•
Retrieves trailing bytes in the receive peripheral-device buffers.
•
Supports programmable data-burst sizes (8, 16, or 32 bytes) and programmable peripheral device data
widths (byte, half-word or word).
•
Supports up to 8191 bytes of data transfer per descriptor. Larger transfers can be performed by chaining
multiple descriptors.