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CHAPTER 12 A/D CONVERTER
User’s Manual U16228EJ2V0UD
255
Notes 1.
Set so that the A/D conversion time is as follows.
Standard products, (A) grade products: 14
μ
s or longer but less than 100
μ
s
(A1) grade products:
(A2) grade products:
2.
A booster circuit is incorporated to realize low-voltage operation. The operation of the circuit that
generates the reference voltage for boosting is controlled by ADCE, and it takes 14
μ
s from operation
start to operation stabilization. Therefore, when ADCS is set to 1 after 14
μ
s or more has elapsed
from the time ADCE is set to 1, the conversion result at that time has priority over the first conversion
result.
14
μ
s or longer but less than 60
μ
s
16
μ
s or longer but less than 48
μ
s
Remark
f
X
: X1 input clock oscillation frequency
Table 12-2. Settings of ADCS and ADCE
ADCS
ADCE
A/D Conversion Operation
0
0
Stop status (DC power consumption path does not exist)
0
1
Conversion waiting mode (only reference voltage generator consumes power)
1
0
Conversion mode (reference voltage generator operation stopped
Note
)
1
1
Conversion mode (reference voltage generator operates)
Note
Data of first conversion cannot be used.
Figure 12-3. Timing Chart When Boost Reference Voltage Generator Is Used
ADCE
Boost reference voltage
ADCS
Conversion
operation
Conversion
operation
Conversion stopped
Conversion
waiting
Boost reference voltage generator: operating
Note
Note
The time from the rising of the ADCE bit to the falling of the ADCS bit must be 14
μ
s or longer to stabilize
the reference voltage.
Cautions 1. A/D conversion must be stopped before rewriting bits FR0 to FR2 to values other than the
identical data.
2. For the sampling time of the A/D converter and the A/D conversion start delay time, see (11)
in 12.6 Cautions for A/D Converter.
3. If data is written to ADM, a wait cycle is generated. Do not write data to ADM when the CPU is
operating on the subsystem clock and the X1 input clock is stopped. For details, see
CHAPTER 34 CAUTIONS FOR WAIT.
Remark
f
X
: X1 input clock oscillation frequency