NXP Semiconductors MC9S12G - Page 552

Analog-to-Digital Converter (ADC12B16CV2)
MC9S12G Family Reference Manual Rev.1.27
554 NXP Semiconductors
16.3.2.12 ATD Conversion Result Registers (ATDDRn)
The A/D conversion results are stored in 16 result registers. Results are always in unsigned data
representation. Left and right justification is selected using the DJM control bit in ATDCTL3.
If automatic compare of conversions results is enabled (CMPE[n]=1 in ATDCMPE), these registers must
be written with the compare values in left or right justified format depending on the actual value of the
DJM bit. In this case, as the ATDDRn register is used to hold the compare value, the result will not be
stored there at the end of the conversion but is lost.
Attention, n is the conversion number, NOT the channel number!
Read: Anytime
Write: Anytime
NOTE
For conversions not using automatic compare, results are stored in the result
registers after each conversion. In this case avoid writing to ATDDRn
except for initial values, because an A/D result might be overwritten.
16.3.2.12.1 Left Justified Result Data (DJM=0)
Table 16-21 shows how depending on the A/D resolution the conversion result is transferred to the ATD
result registers for left justified data. Compare is always done using all 12 bits of both the conversion result
and the compare value in ATDDRn.
Module Base +
0x0010 = ATDDR0, 0x0012 = ATDDR1, 0x0014 = ATDDR2, 0x0016 = ATDDR3
0x0018 = ATDDR4, 0x001A = ATDDR5, 0x001C = ATDDR6, 0x001E = ATDDR7
0x0020 = ATDDR8, 0x0022 = ATDDR9, 0x0024 = ATDDR10, 0x0026 = ATDDR11
0x0028 = ATDDR12, 0x002A = ATDDR13, 0x002C = ATDDR14, 0x002E = ATDDR15
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R
Result-Bit[11:0]
0 000
W
Reset0000000000000000
= Unimplemented or Reserved
Figure 16-14. Left justified ATD conversion result register (ATDDRn)
Table 16-21. Conversion result mapping to ATDDRn
A/D
resolution
DJM conversion result mapping to
ATDDRn
8-bit data 0 Result-Bit[11:4] = conversion result,
Result-Bit[3:0]=0000
10-bit data 0 Result-Bit[11:2] = conversion result,
Result-Bit[1:0]=00
12-bit data 0 Result-Bit[11:0] = result