197
9.3.4
DMA Transfer Types
The DMAC supports the transfers shown in table 9.5. It can operate in single address mode or dual
address mode, which are defined by how many bus cycles the DMAC takes to access the transfer
source and transfer destination. The actual transfer operation timing varies with the bus mode. The
DMAC has two bus modes: cycle-steal mode and burst mode.
Table 9.5
Supported DMA Transfers
Destination
Source
External
Device with
DACK
External
Memory
Memory-
Mapped
External
Device
On-Chip
Memory
On-Chip
Supporting
Module
External device with
DACK
Not available
Single
Single
Not available
Not available
External memory
Single
Dual
Dual
Dual
Dual
Memory-mapped external
device
Single
Dual
Dual
Dual
Dual
On-chip memory
Not available
Dual
Dual
Dual
Dual
On-chip supporting
module
Not available
Dual
Dual
Dual
Dual
Single: Single address mode
Dual: Dual address mode
Address Modes:
•
Single Address Mode
In single address mode, both the transfer source and destination are external; one (selectable) is
accessed by a DACK signal while the other is accessed by an address. In this mode, the
DMAC performs the DMA transfer in 1 bus cycle by simultaneously outputting a transfer
request acknowledge DACK signal to one external device to access it while outputting an
address to the other end of the transfer. Figure 9.6 shows an example of a transfer between an
external memory and an external device with DACK in which the external device outputs data
to the data bus while that data is written in external memory in the same bus cycle.
Summary of Contents for HD6417032
Page 21: ......
Page 35: ...xiv ...
Page 85: ...50 ...
Page 101: ...66 ...
Page 129: ...94 ...
Page 135: ...100 ...
Page 343: ...308 ...
Page 369: ...334 ...
Page 383: ...348 ...
Page 475: ...440 ...
Page 525: ...490 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 18 Self Refresh ...
Page 578: ...543 CK RAS CAS TRp TRc TRcc tRASD1 tRASD2 tCASD3 tCASD2 TRr tCSR Figure 20 62 Self Refresh ...
Page 689: ...654 ...