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ML610Q421/ML610Q422/ML610421 User’s Manual
Chapter 24 RC Oscillation Type A/D Converter
24 – 9
In Table 24-1, mode No.0 and mode No.7 are modes where external clocks to be input to the IN0 or IN1 pin are used
for measurement with the RC oscillator circuit stopped.
As shown in Table 24-1, the two oscillator circuits, RCOSC0 and RCOSC1, are so specified that they cannot operate
concurrenty in order to prevent interference in oscillation from occurring when they oscillate concurrently.
The relationship between an oscillation frequency f
RCCLK
and an RC constant is expressed by the following equation:
1
= t
RCCLK
= k
RCCLK
•R•C
f
RCCLK
where t
RCCLK
is the period of the oscillator clock, k
RCCLK
the proportional constant, and R

C the product of capacitances
CS, CT, (CS+CVR) and (CT+CVR) and resistances RS and RT. CS, CT, (CS+CVR), (CT+CVR), RS, and RT
concern oscillation. The value of k
RCCLK
slightly changes depending on the value of the supply voltage VDD, RI, R,
or C.
Table 24-2 lists the typical k
RCCLK
values.
Table 24-2 Typical Values of the Proportional Constant k
RCCLK
of RC Oscillator Circuits
V
DD
(V) CSn, CTn (pF)
CVR
ｎ
(pF)
RSn, RTn (k
Ω
) k
RCCLK
(Typ.)
3
560 820 100 1.2
560 820 10 1.2
1.5
560 820 100 1.2
560 820 10 1.3
Note) n = 0, 1
Notes:
•
Out of the Port 3 and Port 4 pins, pins that are to be used for the RC-ADC function must be configured as secondary
function input or output using the mode register (P3MOD0, P3MOD1, P4MOD0, P4MOD1) of the corresponding
port.
•
All the Port 3 pins except P35/RCM (see Section 24.1.3, “List of Pins”) are configured as pins dedicated to the
RC-ADC function during A/D conversion. Therefore, during A/D conversion, all the Port 3 pins except P35 cannot
be used as their primary functions in oscillation mode No. 0, 1, 2, 3 or 4, which is selected by the RADMOD register.
In the same way, the P44 to P47 pins of Port 4 cannot be used as their primary functions in oscillation mode No. 5, 6
or 7.