Freescale Semiconductor MC9S12ZVHL32, Reference Manual

Page: 68 / 874

Chapter 1 Device Overview MC9S12ZVHY/MC9S12ZVHL Families
S12ZVHY/S12ZVHL Family Reference Manual Rev. 1.05
68 Freescale Semiconductor
1.14 The ADC0 VRH/VRL
The ADC0 offers two possible sources for both reference voltages VRH[1:0] and VRL[1:0]. On the
MC9S12ZVHY/MC9S12ZVHL Families only VRH[1], VRL[1] sources are connected at device level(to
VDDA, VSSA respectively), the VRH[0], VRL[0] sources are not connected. Thus the application must
set both VRH_SEL and VRL_SEL in the ADC0CCMD_1 to 1.
1.15 The ADC0 Conversion Resolution
The MC9S12ZVHY/MC9S12ZVHL Families only support 10 and 8 bit converstion resolution, although
ADC block guide still has 12 bit related descrition.
1.16 ADC Result Reference
MCUs of the MC9S12ZVHY/MC9S12ZVHL Families are able to measure the internal reference voltage
V
BG
(see Table 1-14 ). V
BG
is a constant voltage with a narrow distribution over temperature and external
voltage supply (see Table A-16 ).
A 10-bit right justified
1
ADC conversion result of V
BG
is provided at address 0x1F_C040/0x1F_C041 in
the NVM’s IFR for reference.The measurement conditions of the reference conversion are listed in
Section A.1.10, “ADC Conversion Result Reference” ” . By measuring the voltage V
BG
(see Table 1-14 )
Table 1-14. ADC0 Channel Assignment
ADC0CMD_1 CH_SEL[5:0]
[5] [4] [3] [2] [1] [0]
Analog Input
Channel
Usage
0 0 1 0 0 0 Internal_0 ADC temperature sensor
0 0 1 0 0 1 Internal_1 Bandgap Voltage V
BG
or
Vreg temperature sensor
V
HT
0 0 1 0 1 0 Internal_2 RESERVED
0 0 1 0 1 1 Internal_3 RESERVED
0 0 1 1 0 0 Internal_4 V
SENSE
or V
SUP
selectable in BATS
module
0 0 1 1 0 1 Internal_5 RESERVED
0 0 1 1 1 0 Internal_6 RESERVED
0 0 1 1 1 1 Internal_7 RESERVED
1. The format of the stored V
BG
reference value is still subject to change.