Functional Overview
The 5407/5404 DMA has been enhanced to expand the DMA reload register sets. Each DMA channel now
has its own DMA reload register set. For example, the DMA reload register set for channel 0 has DMGSA0,
DMGDA0, DMGCR0, and DMGFR0 while DMA channel 1 has DMGSA1, DMGDA1, DMGCR1, and
DMGFR1, etc.
To utilize the additional DMA reload registers, the AUTOIX bit is added to the DMPREC register as shown in
Figure 3−21.
15
14
13
5
8
FREE
AUTOIX
DPRC[5:0]
7
6
0
INT0SEL
DE[5:0]
Figure 3−21. DMPREC Register
Table 3−10. DMA Reload Register Selection
AUTOIX
DMA RELOAD REGISTER USAGE IN AUTO INIT MODE
0 (default)
1
All DMA channels use DMGSA0, DMGDA0, DMGCR0 and DMGFR0
Each DMA channel uses its own set of reload registers
3.12.7 DMA Transfer Counting
The DMA channel element count register (DMCTRx) and the frame count register (DMFRCx) contain bit fields
that represent the number of frames and the number of elements per frame to be transferred.
•
Frame count. This 8-bit value defines the total number of frames in the block transfer. The maximum
number of frames per block transfer is 128 (FRAME COUNT= 0FFh). The counter is decremented upon
the last read transfer in a frame transfer. Once the last frame is transferred, the selected 8-bit counter is
reloaded with the DMA global frame reload register (DMGFR) if the AUTOINIT bit is set to 1. A frame count
of 0 (default value) means the block transfer contains a single frame.
•
Element count. This 16-bit value defines the number of elements per frame. This counter is decremented
after the read transfer of each element. The maximum number of elements per frame is 65536
(DMCTRn = 0FFFFh). In autoinitialization mode, once the last frame is transferred, the counter is reloaded
with the DMA global count reload register (DMGCR).
3.12.8 DMA Transfer in Doubleword Mode
Doubleword mode allows the DMA to transfer 32-bit words in any index mode. In doubleword mode, two
consecutive 16-bit transfers are initiated and the source and destination addresses are automatically updated
following each transfer. In this mode, each 32-bit word is considered to be one element.
3.12.9 DMA Channel Index Registers
The particular DMA channel index register is selected by way of the SIND and DIND fields in the DMA transfer
mode control register (DMMCRn). Unlike basic address adjustment, in conjunction with the frame index
DMFRI0 and DMFRI1, the DMA allows different adjustment amounts depending on whether or not the element
transfer is the last in the current frame. The normal adjustment value (element index) is contained in the
element index registers DMIDX0 and DMIDX1. The adjustment value (frame index) for the end of the frame,
is determined by the selected DMA frame index register, either DMFRI0 or DMFRI1.
The element index and the frame index affect address adjustment as follows:
•
•
Element index: For all except the last transfer in the frame, the element index determines the amount to
be added to the DMA channel for the source/destination address register (DMSRCx/DMDSTx) as
selected by the SIND/DIND bits.
Frame index: If the transfer is the last in a frame, frame index is used for address adjustment as selected
by the SIND/DIND bits. This occurs in both single-frame and multi-frame transfers.
47
November 2001 − Revised April 2004
SPRS007D
TI [ TEXAS INSTRUMENTS ]
