NEC 78K0 User Manual page 223

Notes 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
start to operation stabilization. Therefore, when ADCS is set to 1 after 14
from the time ADCE is set to 1, the conversion result at that time has priority over the first conversion
result.
Remark f : X1 input clock oscillation frequency
X
ADCS ADCE
0 0
0 1
1 0
1 1
Note Data of first conversion cannot be used.
Figure 11-3. Timing Chart When Boost Reference Voltage Generator Is Used
ADCE
Boost reference voltage
ADCS
Note The time from the rising of the ADCE bit to the rising of the ADCS bit must be 14
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 11.6 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.
CHAPTER 30 CAUTIONS FOR WAIT.
Remark f : X1 input clock oscillation frequency
X
CHAPTER 11 A/D CONVERTER
Table 11-2. Settings of ADCS and ADCE
A/D Conversion Operation
Stop status (DC power consumption path does not exist)
Conversion waiting mode (only reference voltage generator consumes power)
Conversion mode (reference voltage generator operation stopped
Conversion mode (reference voltage generator operates)
Boost reference voltage generator: operating
Conversion
Conversion
operation
waiting
Note
User's Manual U16227EJ2V0UD
µ
s or more has elapsed
Note
)
Conversion
Conversion stopped
operation
µ
s or longer to stabilize the
µ
s from operation
For details, see
223