PXS20RM Datasheet, PDF (205/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Analog-to-Digital Converter (ADC)
• At end of the normal conversion chain, Step1 of RC algorithm is executed.
• This process continues for all the Steps of all three algorithms.
• State Machine returns to IDLE state when MCR[NSTART] is cleared.
Instead of starting normal conversion by software (by setting MCR[NSTART]), if it is started by external
trigger, the test channel behaviour will remain same.
In case of Injected conversions, test channel conversion is not performed. It is performed only during
Normal conversions.
If during a test channel conversion, injection conversion arrives, then the test channel is aborted (just as a
normal functional channel) and injected conversions are done. After injected conversions are completed,
the test channel resumes from the Step at which it was aborted. In this case, the MSR.SELF_TEST_S
remains high during the injected conversion.
For self testing, Mode bit should be programmed (atleast one cycle ) BEFORE setting MCR.NSTART bit
and should not be changed thereafter until conversion is ongoing.
9.4.11.3 CTU mode
The CTU mode is enabled by setting MCR[CTUEN]. With this bit set, the CTU operates in control mode.
If CTUEN is set, the test channel conversion can be started only by CTU interface and software cannot
start it. The EN bit in STCR2 register does not have any effect in CTU mode. The CTUEN bit should not
be changed while normal conversion is ongoing.
The interface between CTU and ADC (for Self Test) is shown in Figure 9-50.
CTU
ctu_adc_st_en
ctu_adc_st_step<4:0>
ctu_adc_st_alg <1:0>
ctu_trigger
ctu_nextcmd
ctu_dataout<9:0>
ADC
Figure 9-50. Interface between ADC and CTU to manage self test
For self testing conversions in CTU mode, CTU asserts ctu_adc_st_en signal along with ctu_trigger. The
algorithm and the step number to be executed is put on ctu_adc_st_alg and ctu_adc_st_step respectively.
The other signals ctu_nextcmd, ctu_trigger and ctu_dataout have same meaning as for normal CTU
functional conversion.
Freescale Semiconductor
PXS20 Microcontroller Reference Manual, Rev. 1
9-47