TC1796
System Units (Vol. 1 of 2)
Direct Memory Access Controller
User’s Manual
12-36
V2.0, 2007-07
DMA, V2.0
12.1.9.2 Pattern Detection for 8-bit Data Width
When 8-bit channel data width is selected (CHCRmn.CHDW = 00
B
), the pattern
detection logic is configured as shown in
. Three compare match
configurations are possible.
When 8-bit channel data width is selected, the pattern detection logic makes it possible
to compare the byte of one read move with two different patterns. Furthermore, after
each read move the pattern match result “RDm0 with PATm1, masked by PATm3” is
stored in bit CHCRmn.LXO. This operating mode allows, for example, to detect two-byte
sequences in an 8-bit data stream coming from a serial peripheral unit with 8-bit data
width (e.g.: recognition of carriage-return, line-feed characters). A mask operation of
each compared bit is possible.
Figure 12-25 Pattern Detection for 8-bit Data Width (CHCRmn.CHDW = 00
B
)
Table 12-2
Pattern Detection for 8-bit Data Width
CHCRmn.
PATSEL
Pattern Detection Operating Modes
00
B
Pattern detection disabled
01
B
Pattern compare RDm0 to PATm0, masked by PATm2
10
B
Pattern compare RDm0 to PATm1, masked by PATm3
11
B
Pattern compare RDm0 to PATm0, masked by PATm2 of the actual
read move
and
Pattern compare RDm0 to PATm1, masked by PATm3 of the previous
read move of DMA channel mn
MCA05702
0
31
15
16
RDm3
RDm2
RDm1
RDm0
31
7
0
8
COMP
2
&
PATSEL
CHCRmn
Pattern
Detected
0
LXO
CHSRmn
MEmR
MEmPR
1)
1) Compare result is clocked into LXO after each read move.
Mask
Mask
7
8
23
24
PATm3
PATm2
PATm0
PATm1
COMP
00
01
10
11