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7721 Group User’s Manual

12–16

A-D CONVERTER

12.5 One-shot mode

12.5.2 One-shot mode operation description

(1)

When an internal trigger is selected

The A-D converter starts operation when the A-D conversion start bit is set to “1.”

The A-D conversion is completed after 57 cycles of

φAD. Then, the contents of the successive

approximation register (conversion result) are transferred to the A-D register i.

At the same time as step , the A-D conversion interrupt request bit is set to “1.”

The A-D conversion start bit is cleared to “0” and the A-D converter stops operation.

(2)

When an external trigger is selected

_____

The A-D converter starts operation when the input level to the ADTRG pin changes from “H” to “L”

while the A-D conversion start bit is “1.”

The A-D conversion is completed after 57 cycles of

φAD. Then, the contents of the successive

approximation register (conversion result) are transferred to the A-D register i.

At the same time as step , the A-D conversion interrupt request bit is set to “1.”

The A-D conversion stops.

The A-D conversion start bit remains set to “1” after the operation is completed. Accordingly, the

_____

operation of the A-D converter can be performed again from step when the level of the ADTRG pin

changes from “H” to “L.”

_____

When the level of the ADTRG pin changes from “H” to “L” during operation, the operation at that point

is cancelled and is restarted from step .

Figure 12.5.2 shows the conversion operation in the one-shot mode.

Fig. 12.5.2 Conversion operation in one-shot mode

Trigger occur

Convert input voltage from

ANi pin

Conversion result

A-D register i

A-D conversion interrupt request occurs.

A-D converter halt

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