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Chapter 1 Device Overview MC9S12ZVM-Family
MC9S12ZVM Family Reference Manual Rev. 1.3
Freescale Semiconductor
59
is measured during production test using the internal reference voltage V
BG
, which has a narrow variation
over temperature and external voltage supply. V
BG
is mapped to an internal channel of each ADC module
(
). The resulting 12-bit left justified ADC conversion results of V
BG
are stored to the
flash IFR for reference, as listed in
The measurement conditions of the reference conversion are listed in the device electrical parameters
appendix. By measuring the voltage V
BG
in the application environment and comparing the result to the
reference value in the IFR, it is possible to determine the current ADC reference voltage V
RH
:
The exact absolute value of an analog conversion can be determined as follows:
With:
ConvertedADInput:
Result of the analog to digital conversion of the desired pin
ConvertedReference:
Result of internal channel conversion
StoredReference:
Value in IFR location
n:
ADC resolution (12 bit)
NOTE
The ADC reference voltage V
RH
must remain at a constant level throughout
the conversion process.
1.13.2
SCI Baud Rate Detection
The baud rate for SCI0 and SCI1 is achieved by using a timer channel to measure the data rate on the RXD
signal.
1. Establish the link:
— For SCI0: Set [T0IC3RR1:T0IC3RR0]=0b01 to disconnect IOC0_3 from TIM0 input capture
channel 3 and reroute the timer input to the RXD0 signal of SCI0.
— For SCI1: Set [T0IC3RR1:T0IC3RR0]=0b10 to disconnect IOC0_3 from TIM0 input capture
channel 3 and reroute the timer input to the RXD1 signal of SCI1.
2. Determine pulse width of incoming data: Configure TIM0 IC3 to measure time between incoming
signal edges.
1.13.3
Motor Control Application Overview
The following sections provide information for using the device in motor control applications. These
sections provide a description of motor control loop considerations that are not detailed in the individual
V
RH
StoredReference
ConvertedReference
-------------------------------------------------------
5V
•
=
Result
ConvertedADInput
StoredReference
5V
•
ConvertedReference
2
n
•
------------------------------------------------------------------
•
=