S1C63358 TECHNICAL MANUAL
EPSON
75
CHAPTER 4: PERIPHERAL CIRCUITS AND OPERATION (A/D Converter)
IAD: A/D converter interrupt factor flag (FFF7H•D0)
This flag indicates the status of the A/D converter interrupt.
When "1" is read: Interrupt has occurred
When "0" is read: Interrupt has not occurred
When "1" is written: Flag is reset
When "0" is written: Invalid
IAD is the A/D converter interrupt factor flag that is set when an A/D conversion has finished. The
software can judge from this flag whether there is an A/D converter interrupt or not. This flag is set to "1"
even if the interrupt is masked.
This flag is reset to "0" by writing "1".
After an interrupt occurs, the same interrupt will occur again if the interrupt enabled state (I flag = "1") is
set or the RETI instruction is executed unless the interrupt factor flag is reset. Therefore, be sure to reset
(write "1" to) the interrupt factor flag in the interrupt service routine before shifting to the interrupt
enabled state.
At initial reset, this flag is set to "0".
4.10.7 Programming notes
(1) When supply voltage is 1.6 V or less, it is necessary to set the A/D converter circuit into the V
C2
mode
by writting "1" to VADSEL register befor starting A/D conversion.
(2) The A/D converter can operate by inputting the clock from the clock selector. Therefore, it is neces-
sary to select the clock source and to turn the clock output on before starting A/D conversion. Fur-
thermore, it is also necessary that the OSC3 oscillation circuit is operating when using the OSC3 clock.
(3) When using the OSC3 clock as the A/D conversion clock, do not stop the OSC3 oscillation circuit
during A/D conversion. If the OSC3 oscillation circuit stops, correct A/D conversion result cannot be
obtained.
(4) The input clock and analog input terminals should be set when the A/D converter stops. Changing
these settings in the A/D converter operation may cause errors.
(5) To prevent malfunction, do not start A/D conversion (writing "1" to the ADRUN register) when the
A/D conversion clock is not being output from the clock selector, and do not turn the clock off during
A/D conversion.
(6) If the CHS register selects an input channel which is not included in the analog input terminals set by
the PAD register (the PAD register can select several terminals simultaneously), the A/D conversion
does not result in a correct converted value.
(7) During A/D conversion, do not operate the P4n terminals which are not used for analog inputs of the
A/D converter (for input/output of digital signals). It affects the A/D conversion precision.
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