
R8C/14 Group, R8C/15 Group 16. A/D Converter
Rev.2.10 Jan 19, 2006 Page 176 of 253
REJ09B0164-0210
16.3 Sample and Hold
When the SMP bit in the ADCON2 register is set to “1” (with sample and hold function), A/D conversion
rate per pin increases to 28
φAD cycles for 8-bit resolution or 33φAD cycles for 10-bit resolution. The
sample and hold function is available in all operating modes. Start the A/D conversion after selecting
whether the sample and hold circuit is to be used or not.
When performing the A/D conversion, charge the comparator capacitor in the microcomputer.
Figure 16.6 shows the Timing Diagram of A/D Conversion.
Figure 16.6 Timing Diagram of A/D Conversion
16.4 A/D Conversion Cycles
Figure 16.7 shows the A/D Conversion Cycles.
Figure 16.7 A/D Conversion Cycles
Sampling Time
4ø AD cycle
Sample & Hold
Disabled
Conversion time at the 1st bit at the 2nd bit
Comparison
Time
Sampling Time
2.5ø AD cycle
Comparison
Time
Sampling Time
2.5ø AD cycle
Comparison
Time
* Repeat until conversion ends
Sampling Time
4ø AD cycle
Sample & Hold
Enabled
Conversion time at the 1st bit
at the 2nd bit
Comparison
Time
Comparison
Time
Comparison
Time
* Repeat until conversion ends
Comparison
Time
A/D Conversion Mode
Without Sample & Hold
Without Sample & Hold
With Sample & Hold
With Sample & Hold
8 bits
10 bits
8 bits
10 bits
Conversion
Time
Comparison
Time
Comparison
Time
End process
Sampling
Time
End processConversion time at the 1st bit
Sampling
Time
Conversion time at the 2nd
bit and the follows
49φAD 4φAD 2.0φAD 2.5φAD 2.5φAD 8.0φAD
59φAD 4φAD 2.0φAD 2.5φAD 2.5φAD 8.0φAD
28φAD 4φAD 2.5φAD 0.0φAD 2.5φAD 4.0φAD
33φAD 4φAD 2.5φAD 0.0φAD 2.5φAD 4.0φAD
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