Flow-Through Dma Transfers; Signals; Block Diagram; Flow-Through Dma Transfer Signals - Intel PXA27 Series Design Manual

5.5.2

Flow-Through DMA Transfers

Unlike fly-by DMA transfers, flow-through DMA transfers have no restrictions on transferring
data to either SDRAM partition, external peripherals or companion chips.
5.5.2.1

Signals

See Table 5-3
external logic.
Table 5-3. Flow-Through DMA Transfer Signals
Signal Name
DREQ<2:0>
5.5.2.2

Block Diagram

See Figure 5-3
chip using DMA flow-through transfers. In flow-through mode, a companion chip is addressed as
if the companion chip is a memory device, allowing the companion chip to be the source or the
target of flow-through DMA transfers.
Figure 5-3. Companion Chip Requesting Flow-Through DMA Transfers
®
Intel PXA27x Processor Family Design Guide
for the list of signals required when requesting flow-through DMA transfers from
Type
External Companion Chip Request
The DMA controller detects the positive edge of the DREQ
signal to log a request. The external companion chip
Input asserts the DREQ signal when a DMA transfer request is
required.
Requests on pins DREQ<2:0> are used for data transfers
in flow-through mode.
for illustration showing how to interface the PXA27x processor to a companion
PXA27x Processor
Control
Signals
DMA
Controller Controller
DREQx
Companion Chip
Description
Memory Control Signals
Memory
MD<31:0>
DMA Controller Interface
Memory
Devices
(Static or
Dynamic)
DMA_002_P2
II:5-5