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M30245 Group
(4) Functions selection
(a) Sample & Hold function
Sample & Hold function samples input voltage when A/D conversion starts and carries out A/D con-
version on the voltage sampled. When A/D conversion starts, input voltage is sampled for 3 cycles of
the operation clock. When the Sample & Hold function is selected, set the operation clock for A/D
conversion to 1 MHz or higher.
(b) 8-bit A/D to 10-bit A/D switching function
Either 8-bit resolution or 10-bit resolution can be selected. When 8-bit resolution is selected, the 8
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higher-order bits of the 10-bit A/D are subjected to A/D conversion. The equations for 10-bit resolu-
tion and 8-bit resolution are given below:
10-bit resolution
8-bit resolution
(c) A/D conversion by external trigger
The user can select software or an external pin input to start A/D conversion.
(d) Connecting or cutting Vref
Cutting Vref allows decrease of the current flowing into the A/D converter. To decrease the
microcomputer's power consumption, cut Vref. To carry out A/D conversion, start A/D conversion 1
µs or longer after connecting Vref.
(5) Input to A/D converter and the relation of direction register
To use the A/D converter, set the direction register of the relevant port to input.
(6) Pins related to A/D converter
(a) AN
(b) AVcc pin
(c) V
REF
(d) AVss pin
___________
(e) AD
(7) A/D converter related registers
Figure 2.9.1 shows the memory map of A/D converter-related registers, and Figures 2.9.2 and 2.9.3
show A/D converter-related registers.
Rev.2.00 Oct 16, 2006
REJ09B0340-0200
(Vref X n / 2
(Vref X n / 2
pin through AN
pin
0
7
pin
pin
TRG
page 214 of 354
10
10
) – (Vref X 0.5 / 2
)
8
10
) – (Vref X 0.5 / 2
)
Input pins of the A/D converter
Power source pin of the analog section
Input pin of reference voltage
GND pin of the analog section
Trigger input pin of the A/D converter
2. A/D Converter
(n = 1 to 1023), 0 (n = 0)
(n = 1 to 255), 0 (n = 0)
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