MC9S12P128 Datasheet, PDF (310/564 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Analog-to-Digital Converter (ADC12B10CRev 00.05) Block Description
Table 9-3. ATDCTL1 Field Descriptions (continued)
Field
Description
4
SMP_DIS
Discharge Before Sampling Bit
0 No discharge before sampling.
1 The internal sample capacitor is discharged before sampling the channel. This adds 2 ATD clock cycles to
the sampling time. This can help to detect an open circuit instead of measuring the previous sampled
channel.
3–0
External Trigger Channel Select — These bits select one of the AD channels or one of the ETRIG3-0 inputs
ETRIGCH[3:0] as source for the external trigger. The coding is summarized in Table 9-5.
Table 9-4. A/D Resolution Coding
SRES1
SRES0
A/D Resolution
0
0
8-bit data
0
1
10-bit data
1
0
12-bit data
1
1
Reserved
Table 9-5. External Trigger Channel Select Coding
ETRIGSEL ETRIGCH3 ETRIGCH2 ETRIGCH1 ETRIGCH0 External trigger source is
0
0
0
0
0
AN0
0
0
0
0
1
AN1
0
0
0
1
0
AN2
0
0
0
1
1
AN3
0
0
1
0
0
AN4
0
0
1
0
1
AN5
0
0
1
1
0
AN6
0
0
1
1
1
AN7
0
1
0
0
0
AN8
0
1
0
0
1
AN9
0
1
0
1
0
AN9
0
1
0
1
1
AN9
0
1
1
0
0
AN9
0
1
1
0
1
AN9
0
1
1
1
0
AN9
0
1
1
1
1
1
0
0
0
0
1
0
0
0
1
1
0
0
1
0
1
0
0
1
1
AN9
ETRIG0⁽¹⁾
ETRIG1¹
ETRIG2¹
ETRIG3¹
1
0
1
X
X
Reserved
1
1
X
X
X
Reserved
1. Only if ETRIG3-0 input option is available (see device specification), else ETRISEL is ignored, that means
external trigger source is still on one of the AD channels selected by ETRIGCH3-0
S12P-Family Reference Manual, Rev. 1.12
310
Freescale Semiconductor