MC9S12G FREESCALE [Freescale Semiconductor, Inc], MC9S12G Datasheet - Page 116

• Manufacturer Part Number: MC9S12G
• Description: Ignores external trigger. Performs one conversion sequence and stops.
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Device Overview MC9S12G-Family
1.17
MCUs of the S12G-Family are able to measure the internal reference voltage V
is a constant voltage with a narrow distribution over temperature and external voltage supply (see
Table
A 12-bit left justified
NVM’s IFR for reference.The measurement conditions of the reference conversion are listed in
Section A.15, “ADC Conversion Result
comparing the result to the reference value in the IFR, it is possible to determine the ADC’s reference
voltage V
The exact absolute value of an analog conversion can be determined as follows:
With:
1.18
On all S12G devices except for the S12GA192 and the S12GA240 the external VRH signal is directly
connected to the ADC’s VRH signal input. The ADC’s VRL input is connected to VSSA. (see
Figure
1. The format of the stored V
116
This document is valid for the S12G96 and the S12G128 device. All information related to other devices is preliminary.
A-29).
1-21).
ConvertedADInput:
ConvertedReference:
StoredReference:
n:
ADC Result Reference
RH
ADC VRH/VRL Signal Connection
in the application environment:
To assure high accuracy of the V
not be programmed, erased, or read while the conversion takes place. This
implies that code must be executed from RAM. The “ConvertedReference”
value must be the average of eight consecutive conversions.
The ADC’s reference voltage V
throughout the conversion process.
1
ADC conversion result of V
DDF
Result
reference value is still subject to change.
Result of the analog to digital conversion of the desired pin
Result of channel “Internal_0” conversion
Value in IFR locatio 0x0_4022/0x0_4023
ADC resolution (10 bit)
MC9S12G Family Reference Manual,
=
ConvertedADInput
V
RH
Reference”. By measuring the voltage V
=
------------------------------------------------------------ - 5V
ConvertedReference
StoredReference
RH
CAUTION
CAUTION
DDF
must remain at a constant level
DDF
reference conversion, the NVMs must
•
------------------------------------------------------------------------ -
ConvertedReference 2
is provided at address 0x0_4022/0x0_4023 in the
StoredReference 5V
•
Rev.1.01
•
•
n
DDF
DDF
(see
Freescale Semiconductor
(see
Table
Table
1-31). V
1-31) and
DDF