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TC1796

System Units (Vol. 1 of 2)

Direct Memory Access Controller

User’s Manual 12-19 V2.0, 2007-07

DMA, V2.0

Figure 12-12 Programmable Address Modification - Example 2

12.1.4.7 Circular Buffer

Destination and source address can be configured to build a circular buffer separately

for source and destination data. Within this circular buffer, addresses are updated as

defined in Figure 12-11 and Figure 12-12 with a wrap-around at the buffer limits. The

circular buffer length is determined by bit fields ADRCRmn.CBLS (for the source buffer)

and ADRCRmn.CBLD (for the destination buffer). These 4-bit wide bit fields determine

which bits of the 32-bit address remain unchanged at an address update. Possible buffer

sizes of the circular buffers can be 2

CBLS

or 2

CBLD

bytes (= 1, 2, 4, 8, 16, … up to 32k

bytes).

When source or destination addresses are updated (incremented or decremented) after

a DMA move, all upper bits [31:CBLS] of source address and [31:CBLD] of destination

address are frozen and remain unchanged, even if a wrap-around from the lower

address bits [CBLS:0] or [CBLD:0] occurred. This address-freezing mechanism always

causes the circular buffers to be aligned to a multiple integer value of its size.

If the circular buffer size is less or equal than the selected address offset (see

Table 12-8), the same circular buffer address will always be accessed.

MCA05691

ADRCRmn Parameters:

SMF = 000

INCS = 1

Source Memory Destination Memory

31 01516

DMA

Moves

31 01516

ADRCRmn Parameters:

DMF = 001

INCD = 1

D2D3

D4D5

D6D7

Infineon Technologies TC1796 User Manual

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