AN1740 Freescale Semiconductor / Motorola, AN1740 Datasheet - Page 66

• Manufacturer Part Number: AN1740
• Description: Applications Using the Analog Subsystem on MC68HC05JJ/JP Series Microcontrollers
• Manufacturer: Freescale Semiconductor / Motorola

Application Note
Use of Conversion
Flags
66
The most important considerations in using the automated mode 2 or
mode 3 is that the TOF, OCF, and ICF flags can get set without any
enabling control and that they can start getting set before the software is
ready to use them. This means that modes 2 or 3 can operate as either
interrupt-driven or free-running software.
It is highly recommended that modes 2 and 3 use conversion status flags
such as EOC and CIP as described on page
allow the timer interrupt service routine to determine if the conversions
are executing properly or if a fault has occurred. These flags should be
contained in an assigned RAM location. Avoid using the CHG bit in the
ACR or the CPF2 or CMP2 bits in the ASR for these purposes, since
they can be set automatically by hardware events that are not under the
user’s direct software control.
Freescale Semiconductor, Inc.
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a. Once set, the ICF bit must be reset by the proper software
b. Once set, the ICF will lock out any future input captures until
c. The ICF flag overrides the TOF or OCF flags. If a TOF or OCF
d. The ICF can be triggered by a positive or negative going edge
e. The trigger source for the ICF can be either the signal on PB3
sequence of reading the TSR, then the ICRL.
the ICF flag bit is cleared.
is present when the ICF is cleared, the charging of the PB0 pin
will begin immediately.
depending on the state of the IEDG bit in the TCR.
or the output of voltage comparator 2 dependent on the state
of the ICEN bit in the ACR.
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and 58. These flags
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AN1740