
IDT DMA Controller
PES32NT24xG2 User Manual
15 - 7
January 30, 2013
Notes
All DMA descriptors share the same common format shown in Figure 15.7.
1
–
DMA descriptors are eight DWords in size.
–
DMA descriptors must be DWord aligned. Processing by a channel of a DMA descriptor with an
unaligned DWord address results in an error.
–
A DMA descriptor must not be placed at memory address 0x0, as this address is used to indicate
the end of a descriptor list.
–
DMA descriptors must not cross a 4-KB address boundary. Processing by a channel of a DMA
descriptor that violates this rule produces undefined behavior.
–
The Descriptor Type (DTYPE) field specifies the type of the descriptor that indicates to the DMA
channel how descriptor specific fields should be interpreted and the processing that should be
performed by the DMA channel.
–
The Descriptor Status (DSTS) field specifies the status of the descriptor. A value of zero indicates
that the descriptor has not been processed. A value other than zero indicates that the descriptor
has been processed by a DMA channel and indicates the stopping condition (e.g., successful
completion or error).
–
The Next Lower (NEXTL) and Next Upper (NEXTU) fields together form a 64-bit address that indi-
cates the address of a next descriptor in a descriptor list. A value of zero indicates that this is the
last descriptor in a descriptor list.
Figure 15.7 General DMA Descriptor Format
When a DMA channel completes processing of a descriptor, it writes back DWord zero with updated
status information.
There are two descriptor types supported by the DMA channel. Stride control descriptors are used to
modify stride control parameters while data transfer descriptors are used to perform data movement opera-
tions.
Stride Control Descriptor
A stride control descriptor is used to modify DMA channel stride parameters, no data is transferred in
processing of a stride control descriptor.
–
The values loaded by a stride control descriptor are used by all subsequent data transfer descrip-
tors until the processing of the next stride control descriptor.
The format of a stride control descriptor is shown in Figure 15.8 and the fields are described in Table
15.4. Following the PCI convention, the format is shown in little-endian.
1.
Following the PCI convention, the descriptor layout is shown in little-endian.
31
DSTS
24 23
16 15
8
7
0
DTYPE
NEXTL
NEXTU
0
1
2
3
4
5
6
7
I
O
F
Summary of Contents for PCI Express 89HPES32NT24xG2
Page 20: ...IDT Table of Contents PES32NT24xG2 User Manual x January 30 2013 Notes...
Page 24: ...IDT List of Tables PES32NT24xG2 User Manual xiv January 30 2013 Notes...
Page 28: ...IDT List of Figures PES32NT24xG2 User Manual xviii January 30 2013 Notes...
Page 56: ...IDT PES32NT24xG2 Device Overview PES32NT24xG2 User Manual 1 20 January 30 2013 Notes...
Page 100: ...IDT Switch Core PES32NT24xG2 User Manual 4 22 January 30 2013 Notes...
Page 128: ...IDT Failover PES32NT24xG2 User Manual 6 4 January 30 2013 Notes...
Page 148: ...IDT Link Operation PES32NT24xG2 User Manual 7 20 January 30 2013 Notes...
Page 164: ...IDT SerDes PES32NT24xG2 User Manual 8 16 January 30 2013 Notes...
Page 170: ...IDT Power Management PES32NT24xG2 User Manual 9 6 January 30 2013 Notes...
Page 196: ...IDT Transparent Switch Operation PES32NT24xG2 User Manual 10 26 January 30 2013 Notes...
Page 244: ...IDT SMBus Interfaces PES32NT24xG2 User Manual 12 40 January 30 2013 Notes...
Page 247: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 3 January 30 2013 Notes...
Page 248: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 4 January 30 2013 Notes...
Page 330: ...IDT Switch Events PES32NT24xG2 User Manual 16 6 January 30 2013 Notes...
Page 342: ...IDT Multicast PES32NT24xG2 User Manual 17 12 January 30 2013 Notes...
Page 344: ...IDT Temperature Sensor PES32NT24xG2 User Manual 18 2 January 30 2013 Notes...
Page 384: ...IDT Register Organization PES32NT24xG2 User Manual 19 40 January 30 2013...
Page 492: ...IDT Proprietary Port Specific Registers PES32NT24xG2 User Manual 21 44 January 30 2013 Notes...
Page 588: ...IDT NT Endpoint Registers PES32NT24xG2 User Manual 22 96 January 30 2013 Notes...
Page 710: ...IDT JTAG Boundary Scan PES32NT24xG2 User Manual 25 12 January 30 2013 Notes...
Page 743: ...IDT Usage Models PES32NT24xG2 User Manual 26 33 January 30 2013 Notes...
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