Pci Controller Dma; Pci Byte Enables For Sub-Word Single Ahb Read/Write Cycles - Intel IXP45X Developer's Manual

Table 198.

PCI Byte Enables for Sub-word Single AHB Read/write Cycles

AHB addr[1:0]
00
01
10
11
00
01
10
11
00
01
10
11
00
01
10
11
10.3.3

PCI Controller DMA

The IXP45X/IXP46X network processors contain two channels that can be used for DMA
(Direct Memory Accesses) to/from the PCI bus and the AHB. The DMA Controller
function provides two channels of DMA capability to off load, from the Intel XScale
processor, large data transfers between the PCI bus and AHB.
The DMA channels are unidirectional: one DMA channel is used for PCI-to-AHB transfers
and one DMA channel is used for AHB-to-PCI transfers. The DMA transfers are
implemented using three of the PCI Controller Configuration and Status Registers to
specify the PCI address, the AHB address, and the transfer length/control. Each DMA
channel has two sets of three registers to provide buffering for consecutive transfers.
For each direction, when a DMA channel is executing one transfer using the active DMA
register set, the other DMA register set can be set-up by the Intel XScale processor to
specify the next transfer. Both DMA channels can run concurrently so that individual
PCI-to-AHB transfers and AHB-to-PCI transfers that make up the DMA transfers are
interleaved on the AHB and PCI bus.
Individual DMA-complete and DMA-error status indication is provided for each channel
using the DMA Control Register (PCI_DMACTRL) with an interrupt that may be
optionally generated in each case.
The DMA channels share resources with the AHB Master and Slave interfaces and
therefore must arbitrate for these resources. AHB-to-PCI DMA transfers use the AHB
Master Interface, the PCI Initiator Request, and Initiator Transmit FIFOs. PCI-to-AHB
DMA transfers use the AHB Master Interface, the PCI Initiator Request FIFO, and
Initiator Receive FIFO. Use of the AHB Master Interface will revolve between the two
DMA channels and PCI requests that appear in the Target Receive FIFO.
® ®
Intel IXP45X and Intel IXP46X Product Line of Network Processors
Develepor's Manual
536
® ®
Intel IXP45X and Intel
pci_csr.ABE
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
IXP46X Product Line of Network Processors—PCI Controller
pci_csr.ADS
8-bit transfer
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
PCI Byte Enable [3:0]
16-bit transfer
1110 1100
1101 1100
1011 0011
0111 0011
0111 0011
1011 0011
1101 1100
1110 1100
0111 0011
1011 0011
1101 1100
1110 1100
1110 1100
1101 1100
1011 0011
0111 0011
August 2006
Order Number: 306262-004US