Chapter 23 Analog-to-Digital Converter (ADC)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
587
23.3.4
ADC CTU (Cross Triggering Unit)
23.3.4.1
Overview
The ADC cross triggering unit (CTU) is added to enhance the injected conversion capability of the ADC.
The CTU contains multiple event inputs that can be used to select the channels to be converted from the
appropriate event configuration register. The CTU generates a trigger output pulse of one clock cycle and
outputs onto an internal data bus the channel to be converted. A single channel is converted for each
request. After performing the conversion, the ADC returns the result on internal bus.
The conversion result is also saved in the corresponding data register and it is compared with watchdog
thresholds if requested.
The CTU can be enabled by setting MCR[CTUEN].
The CTU and the ADC are synchronous with the MC_PLL_CLK in both cases.
23.3.4.2
CTU in control mode
In CTU control mode, the CPU is able to write in the ADC registers but it cannot start any conversion.
Conversion requests can be generated only by the CTU trigger pulse. If a normal or injected conversion is
requested, it is automatically discarded.
When a CTU trigger pulse is received with the injected channel number, the conversion starts. The
CTUSTART bit is set automatically at this point and it is also automatically reset when CTU Control mode
is disabled (CTUEN = ‘0’).
16
0.063
9
1
0.500
8.000
1
0.625
0
1.188 19.000
32
0.031
17
1
0.500
16.000
2
0.625
1
1.156 37.000
1
Where: INPSAMPLE
3
2
Where: INPSAMP
6, N = 0.5; INPSAMP > 6, N = 1
3
Where: T
sample
= (INPSAMP-N)T
ck
; Must be
500 ns
Table 23-3. Max/Min ADC_clk frequency and related configuration settings at 5 V / 3.3 V for ADC0
INPCMP
INPLATCH
Max f
ADC_clk
Min f
ADC_clk
00/01
0
20+4%
6
1
—
—
10
0
—
—
1
32+4%
6
11
0
—
—
1
32+4%
9
Table 23-2. ADC sampling and conversion timing at 5 V / 3.3 V for ADC0 (continued)
Clock
(MHz)
T
ck
(
s)
INPSAMPLE
1
Ndelay
2
T
sample
3
T
sample
/T
ck
INPCMP
T
eval
(
s)
INPLATCH
T
conv
(
s)
T
conv
/
T
ck