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µ PD78214 Sub-Series
Fig. 8-10 Example of Malfunction in a Hardware-Started A/D Conversion
Conversion trigger
A/D converter
operatioon
INTAD
Notes 1. When the operation is normal, the result of conversion 2 is stored. If a malfunction occurs, however, value 7FH is stored.
2. Time from when an input to the INT5 pin changes to when its edge is asserted. See Chapter 11 for details.
In order to solve this problem, the A/D converter mode register (ADM) must be set again after the necessary A/D conversion
is hardware-started and completed. A similar problem occurs during in-circuit emulation.
3. Digital noise at the INTP6 pin cannot be eliminated normally with an in-circuit emulator. If it has been specified that A/D
conversion be hardware-started, A/D conversion may be started by an erroneously detected edge. See Section 11.4 for detail
on erroneous detection of an edge.
(1) Select-mode A/D conversion
The analog signal at the input pin, specified in the ADM register, is converted to digital form. When one
A/D conversion sequence is completed, the analog signal at the same input pin is converted again. Each time
a conversion sequence is completed, an interrupt request (INTAD) is generated.
If a valid edge arrives at the INTP5 pin during A/D conversion, the current conversion sequence is stopped,
and another conversion session is started.
236
INTP5
Note 2
ADCR
Conversion 1
Conversion 2
Conversion
result 1
Note 1
7FH
Conversion completion and
conversion trigger occur
simultaneously
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