MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor
19-15
19.3.2.3
eQADC External Trigger Digital Filter Register (EQADC_ETDFR)
The EQADC_ETDFR is used to set the minimum time a signal must be held in a logic state on the CFIFO
triggers inputs to be recognized as an edge or level gated trigger. The digital filter length field specifies the
minimum number of system clocks that must be counted by the digital filter counter to recognize a logic
state change.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg Addr
Base + 0x000C
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
R
0
0
0
0
0
0
0
0
0
0
0
0
DFL
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Reg Addr
Base + 0x000C
Figure 19-4. eQADC External Trigger Digital Filter Register (EQADC_ETDFR)
Table 19-5. EQADC_ETDFR Field Description Table
Bits
Name
Description
0–27
—
Reserved.
28–31
DFL
[0:3]
Digital filter length. Specifies the minimum number of system clocks that must be counted
by the digital filter counter to recognize a logic state change. The count specifies the
sample period of the digital filter which is calculated according to the following equation:
Minimum clock counts for which an ETRIG signal needs to be stable to be passed through
the filter are shown in
. Refer to
Section 19.4.3.4, “External Trigger Event
,” for more information on the digital filter.
Note: The DFL field must only be written when the MODEn of all CFIFOs are configured
to disabled.
Table 19-6. Minimum Required Time to Valid ETRIG
DFL[0:3]
Minimum Clock Count
Minimum Time (ns)
(System Clock = 120MHz)
0b0000
2
16.67
0b0001
3
25.00
0b0010
5
41.67
0b0011
9
75.00
0b0100
17
141.67
0b0101
33
275.00
0b0110
65
541.67
FilterPeriod
S
ystemClockPeriod
2
DFL
1 S
ystemClockPeriod
+
=
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