C508_01 Datasheet, PDF (194/267 Pages) Infineon Technologies AG – 8-Bit CMOS Microcontroller

C508
On-Chip Peripheral Components
The duration of an A/D conversion is a multiple of the period of the f_IN clock signal. The
calculation of the A/D conversion time is shown in the next section.
6.5.4 A/D Conversion Timing
An A/D conversion is started by writing into the SFR ADDATL with dummy data. A write
to SFR ADDATL will start a new conversion even if a conversion is currently in progress.
The conversion begins with the next machine cycle, and the BSY flag in SFR ADCON0
will be set.
The A/D conversion procedure is divided into three parts:
– Sample phase (t_S), used for sampling the analog input voltage.
– Conversion phase (t_CO), used for the real A/D conversion (includes calibration).
– Write result phase (t_WR), used for writing the conversion result into the ADDAT
registers.
The total A/D conversion time is defined by t_ADCC which is the sum of the two phase
times t_S and t_CO. The duration of the three phases of an A/D conversion is specified by
their corresponding timing parameter as shown in Figure 6-51.
Start of an
AD conversion
Result is written
into ADDAT
BSY Bit
Sample
Phase
Conversion Phase
t_S
t_CO
t_ADCC
A/D Conversion Time Cycle Time
t_ADCC = t_S + t_CO
PS = Prescaler value
Write
t_WR
Result
Phase
t_WR = t_IN
Prescaler Ratio
(= PS)
32
16
8
4
t_S
64 x t_IN
32 x t_IN
16 x t_IN
8 x t_IN
t_CO
320 x t_IN
160 x t_IN
80 x t_IN
40 x t_IN
t_ADCC
384 x t_IN
192 x t_IN
96 x t_IN
48 x t_IN
MCT04078
Figure 6-51 A/D Conversion Timing
User’s Manual
6-129
2001-05