R01UH0822EJ0100 Rev.1.00
Page 831 of 1041
Jul 31, 2019
RX13T Group
26. 12-Bit A/D Converter (S12ADF)
26.2.13
A/D Sampling State Register n (ADSSTRn) (n = 0 to 7, O)
The ADSSTRn register sets the sampling time for analog input.
If one state is one ADCLK (A/D conversion clock) cycle and the ADCLK clock is 32 MHz, one state is 31.25 ns. The
initial value is 13 states. If the impedance of analog input signal source is too high to secure sufficient sampling time or if
the ADCLK clock is slow, the sampling time can be adjusted. The ADSSTRn register should be set while the
ADCSR.ADST bit is 0. The lower-limit value for sampling time differs depending on the PCLK to ADCLK frequency
ratio.
Set a value that is 5 states or more when PCLK to ADCLK frequency ratio = 1:1, 2:1, 4:1, or 8:1.
shows the relationship between the A/D sampling state register and the relevant channels.
For details, refer to
section 26.3.5, Analog Input Sampling Time and Scan Conversion Time
.
Table 26.9
Relationship between A/D Sampling State Register and Relevant Channels
Note 1. When performing A/D conversion of the internal reference voltage, the sampling time should be 5 μs or longer.
Address(es): S12AD.ADSSTR0 0008 90E0h, S12AD.ADSSTR1 0008 90E1h, S12AD.ADSSTR2 0008 90E2h,
S12AD.ADSSTR3 0008 90E3h, S12AD.ADSSTR4 0008 90E4h, S12AD.ADSSTR5 0008 90E5h,
S12AD.ADSSTR6 0008 90E6h, S12AD.ADSSTR7 0008 90E7h,
S12AD.ADSSTRO 0008 90DFh
b7
b6
b5
b4
b3
b2
b1
b0
Value after reset:
0
0
0
0
1
1
0
1
Unit
Register Name
Relevant Channels
S12AD
ADSSTR0 register
AN000, Self-Diagnosis
ADSSTR1 register
AN001
ADSSTR2 register
AN002
ADSSTR3 register
AN003
ADSSTR4 register
AN004
ADSSTR5 register
AN005
ADSSTR6 register
AN006
ADSSTR7 register
AN007
ADSSTRO register
Internal reference voltage*