Enhanced Queued Analog-to-Digital Converter (eQADC)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
31-40
Freescale Semiconductor
Preliminary
data received from the ADC and the calibration constants GCC and OCC (See
”). Then, this 14-bit data is further formatted into a 16-bit format
according to the status of the FMT bit in the conversion command. When FMT is asserted, the
14-bit result data is reformatted to look as if it was measured against an imaginary ground at
VREF/2 (the msb (most significant bit) bit of the 14-bit result is inverted), and is sign-extended to
a 16-bit format as in
. When FMT is negated, the eQADC zero-extends the 14-bit
result data to a 16-bit format as in
. Correspondence between the analog voltage in a
channel and the calculated digital values is shown in
.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
SIGN_EXT
CONVERSION_RESULT (With inverted msb bit)
0
0
ADC Result
Figure 31-25. ADC Result Format when FMT = 1 (Right Justified Signed)—On-Chip ADC Operation
Table 31-29. ADC Result Format when FMT = 1 Field Descriptions
Field
Description
SIGN_EXT
Sign Extension. Only has meaning when FMT is asserted. SIGN_EXT is 0b00 when CONVERSION_RESULT
is positive, and 0b11 when CONVERSION_RESULT is negative.
CONVERSION
_RESULT
Conversion Result. A digital value corresponding to the analog input voltage in a channel when the conversion
command was initiated. The two’s complement representation is used to express negative values.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
0
0
CONVERSION_RESULT
0
0
ADC Result
Figure 31-26. ADC Result Format when FMT = 0 (Right Justified Unsigned)—On-Chip ADC Operation
Table 31-30. ADC Result Format when FMT = 0 Field Descriptions
Field
Description
SIGN_EXT
Sign Extension. Only has meaning when FMT is asserted. SIGN_EXT is 0b00 when CONVERSION_RESULT
is positive, and 0b11 when CONVERSION_RESULT is negative.
CONVERSION
_RESULT
Conversion Result. A digital value corresponding to the analog input voltage in a channel when the conversion
command was initiated.
