TC1796
System Units (Vol. 1 of 2)
Direct Memory Access Controller
User’s Manual 12-37 V2.0, 2007-07
DMA, V2.0
12.1.9.3 Pattern Detection for 16-bit Data Width
When 16-bit channel data width is selected (CHCRmn.CHDW = 01
B
) the pattern
detection logic can be configured as shown in Figure 12-26. Three compare match
configurations are possible.
When 16-bit channel data width is selected, the pattern detection logic makes it possible
to compare the complete half-word of one read move only (aligned mode) or to compare
upper and lower byte of two consecutive read moves (un-aligned modes). Both modes
can be combined, too (combined mode). A mask operation of each compared bit is
possible.
In un-aligned mode 1 (source address decremented), the high byte (RDm1) of the
current and the low byte (RDm0) of the previous 16-bit read move are compared.
In un-aligned mode 2 (source address incremented), the low byte (RDm0) of the current
and the high byte (RDm1) of the previous 16-bit read move are compared.
If it is not known on which byte boundary (even or odd address) the 16-bit pattern to be
detected is located, the combined mode should be used. This mode is the most flexible
mode that combines the pattern search capability for aligned and un-aligned 16-bit data
searches.
Table 12-3 Pattern Detection for 16-bit Data Width
CHCRmn.
PATSEL
ADRCRmn.
INCS
Pattern Detection Operating Modes
00
B
– Pattern detection disabled
01
B
– Aligned Mode:
Pattern compare RDm[1:0] to PATm[1:0], masked by
PATm[3:2]
10
B
0 Un-aligned Mode 1 (Source Address Decrement):
Pattern compare RDm1 to PATm0, masked by PATm2 of
the actual read move and
Pattern compare RDm0 to PATm1, masked by PATm3
(LXO) of the previous read move of DMA channel mn
1 Un-aligned Mode 2 (Source Address Increment):
Pattern compare RDm0 to PATm1, masked by PATm3 of
the actual read move and
Pattern compare RDm1 to PATm0, masked by PATm2
(LXO) of the previous read move of DMA channel mn
11
B
0 or 1 Combined Mode:
Pattern compare for aligned mode (PATSEL = 01
B
)
or un-aligned modes (PATSEL = 10
B
)
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