
IDT DMA Controller
PES32NT24xG2 User Manual
15 - 17
January 30, 2013
Notes
Figure 15.11 DMA Chaining Example
Writing to the DMACxNDPTRL/H registers while the DMA is running (i.e., the RUN bit is set in the
DMACxCTL register) simply modifies the register value. Writing a non-zero value to the DMACxNDPTRL/H
registers while the DMA is not running (i.e., the RUN bit is cleared) and the Error (E) bit is cleared in the
DMACxSTS register not only modifies the register value, but also causes a descriptor chaining operation to
take place.
–
The DMACxDPTRL/H register is loaded with the value in the DMACxNDPTRL/H register
–
The contents of the DMACxNDPTRL and DMACxNDPTRH registers are set to zero.
–
The Chain (C) bit is set in the DMACxSTS register.
–
The DMA controller starts processing descriptors starting with the descriptor pointed to by the
DMACxDPTRL/H registers.
Automatic execution of a descriptor chaining operation may be disabled. This provides a race-free
mechanism for software to update the DMA Channel Next Descriptor Pointer registers (DMACxNDPTRH/L)
with a 64-bit value while the DMA is running.Initiation of a descriptor chaining operation as a side effect of
writing to the DMACxNDPTRL register may be disabled by setting the Disable DMACxNDPTRL Descriptor
Processing Initiation (DISANDPTRL) bit in the DMA Channel Configuration (DMAxCFG) register.
Execution of a descriptor chaining operation as a side effect of writing to the DMACxNDPTRL register
may be disabled by setting the Disable DMACxNDPTRL Descriptor Processing Initiation (DISNDPTRL) bit
in the DMA Channel Configuration (DMAxCFG) register.
Execution of a descriptor chaining operation as a side effect of writing to the DMACxNDPTRH register
may be disabled by setting the Disable DMACxNDPTRH Descriptor Processing Initiation (DISNDPTRH) bit
in the DMA Channel Configuration (DMAxCFG) register.
Table 15.7 shows the behavior of the DMA with respect to the setting of the DISNDPTRH and
DISNDPTRL bits in the DMACxCFG register.
DMAxCFG.
DISNDPTRH
DMAxCFG.
DISNDPTRL
DMA Chaining Behavior
0
0
Execute DMA chaining if (DMACxNDPTRH != 0) or (DMACxNDP-
TRL != 0)
0
1
Execute DMA chaining if (DMACxNDPTRH != 0)
1
0
Execute DMA chaining if (DMACxNDPTRL != 0)
1
1.
The DMACxNDPTRL and DMACxNDPTRH registers must never be written with the value of 0x0. Doings so produces an
undefined operation.
1
1
DMA Chaining is disabled
Table 15.7 DMA Chaining Disabling
DMAxDPTRH / DMAxDPTRL
Descriptor
A
Descriptor
B
Descriptor
C
Descriptor
D
DMAxNDPTRH / DMAxNDPTRL
Descriptor
W
Descriptor
X
Descriptor
Y
Descriptor
Z
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...
Page 744: ...IDT Usage Models PES32NT24xG2 User Manual 26 34 January 30 2013 Notes...