Chapter 8 DMA Controller
8-18
8.3.10 Chain
DMA
Transfer
Table 8.3.4 shows the data structure in memory that the DMA Command Descriptor has. When the
Simple Chain bit (SMPCHN) of the DMA Channel Control Register (DMCCRn) is set, only the initial
four double words are used. DMSAIRn, DMDAIR, DMCCRn, and DMCSRn use the settings from
when DMA started. In addition, all eight double words are used when the Simple Chain bit (SMPCHN)
is cleared.
Saving the start memory address of another DMA Command Descriptor in the Offset 0 Chain
Address field makes it possible to construct a chain list of DMA Command Descriptors (Figure 8.3.5).
Set “0” in the Chain Address field of the DMA Command Descriptor at the end of the chain list.
When DMA transfer that is specified by one DMA Command Descriptor ends, the DMA Controller
automatically reads the next DMA Command Descriptor indicated by the Chain Address Register
(Chain transfer), then continues DMA transfer. Continuous DMA transfer that uses multiple Descriptors
connected into such a chain-like structure is called Chain DMA transfer.
Since the DMA Channel Status Register is also overwritten during Chain transfer when the DMA
Simple Chain bit (SMPCHN) is cleared, be sure not to unnecessarily clear necessary bits.
Placing DMA Command Descriptors at addresses that do not span across 32-double-word boundaries
in memory is efficient since they are read by one G-Bus Burst Read operation.
Table 8.3.4 DMA Command Descriptors
Offset Address
Field Name
Transfer Destination Register
0x00
Chain Address
DMA Chain Address Register (DMCHARn)
0x08
Source Address
DMA Source Address Register (DMSARn)
0x10
Destination Address
DMA Destination Address Register (DMDARn)
0x18
Count
DMA Count Register (DMCNTRn)
0x20
Source Address Increment
DMA Source Address Increment Register (DMSAIRn)
0x28
Destination Address Increment
DMA Destination Address Increment Register (DMDAIRn)
0x30
Channel Control
DMA Channel Control Register (DMCCRn)
0x38
Channel Status
DMA Channel Status Register (DMCSRn)
Summary of Contents for TX49 TMPR4937
Page 1: ...64 Bit TX System RISC TX49 Family TMPR4937 Rev 2 0 ...
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Page 13: ...Table of Contents ix TMPR4937 Revision History 1 ...
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Page 15: ...Handling Precautions ...
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Page 18: ...1 Using Toshiba Semiconductors Safely 1 2 ...
Page 40: ...3 General Safety Precautions and Usage Considerations 3 18 ...
Page 42: ...4 Precautions and Usage Considerations 4 2 ...
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Page 156: ...Chapter 7 External Bus Controller 7 56 ...
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