Rohm LAPIS SEMICONDUCTOR ML620Q503, User Manual

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ML620Q503/Q504 User's Manual
Chapter 24 RC Oscillation Type A/D Converter
FEUL620Q504 24-15
Figure 24-6 Operation Timing in Counter A Reference Mode
(2) Operation in Counter B reference mode
Figure 24-7 shows the operation timing in Counter B reference mode.
Following is an example of operation procedure in Counter B reference mode:

Preset to Counter B (RADCB0 and RADCB1) the value obtained by subtracting the count value “nB1”
from the maximum value + 1 (1000000H). The product of the count value “nB1” and the RCCLK clock
cycle indicates the gate time.
k
Preset “000000H” in Counter A (RADCA0 and RADCA1).
l
Set the OM3–OM0 bits of RADMOD to desired oscillation mode. (See Table 24-1)

Set the RADI bit of RADMOD to “1” to specify generating of an interrupt request signal by Counter B
overflow.
n
Set the RARUN bit of RADCON to “1” to start A/D conversion.
When the RARUN bit is set to “1” and the RCON signal (signal synchronized with the fall of the base clock) is
set to”1”, the RC oscillator circuit starts operation and Counter B starts counting of the RC oscillator clock
(RCCLK). When Counter B overflows, the RARUN bit is automatically reset (
o
) and conversion operation
terminates. At the same time, an RC-ADC interrupt request (RADINT) occurs. (
p
)
RARUN
BSCLK
t
BSCLK
RCON
Counter A
(100000H-nA0) (+1) (+2) (+3) 0FFFFFCH 0FFFFFDH 0FFFFFEH 0FFFFFFH 0000000H
Overflow
000000H 000001H 000002H nB0-2 nB0-1 nB0
RCCLK
Counter B
CR oscillator circuit
Input waveform
IN0/IN1
t
RCCLK
Gate time
nA0 • t
BSCLK
nB0 • t
RCCLK
RADINT

(Interrupt)
Request




nA0 : Reference count value
nB0 : Measurement count