Fujitsu FR81S User Manual
CHAPTER 44: 12-BIT A/D CONVERTER
6. Notes
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER
: 12-BIT A/D CONVERTER
FUJITSU SEMICONDUCTOR CONFIDENTIAL
117
6. Notes
This section explains notes.
Notes on Using A/D Activation Compare
Configuration of select
Be sure to configure select while the free-run timer is inactive.
Configuration of protection of A/D data register
It is necessary to set the PRT bit and the PRTS bit before the A/D conversion starts. It is not allowed to set
this bit during the A/D conversion and the state that the A/D data register is being protected.
When cancelling the protection function of the A/D data register, you execute the protection cancellation
which is set in the PRTS bit after the A/D conversion stops, or you disable the protection function by the
PRT bit.
If the PRTS bit is changed while the A/D data register is being protected, it is necessary to execute the
protection cancellation operation which is set in the PRTS bit (for example reading of the A/D data register,
or clearing operation by writing "0" to an interrupt request flag bit) after changing the PRTS bit in order to
cancel the A/D data register protection. For example PRTS is set to 0 after clearing an interrupt request flag
bit while PRT=1 and PRTS=1, and the A/D data register is being protected, it is needed to read the A/D data
register and clear by writing "0" to the interrupt request flag bit again in order to cancel the protection.
Compare match activation
If the compare register (ADCOMP) is set to 0x0000 or the same value as the value set in the compare clear
register of the free-run timer, an A/D activation request signal will be generated when a compare match is
detected, regardless of whether the setting of the counting direction select bits (SEL0 and SEL1) of the A/D
activation trigger control register (ADTCS) specifies counting-up or counting-down.
Setting of the counting direction select bits of the A/D activation trigger
control status register
When the free-run timer is in the up count mode, the counting direction select bits SEL0 and SEL1 of the
A/D activation trigger control status register (ADTCS) must not be set respectively to "1" and "0" (only
counting down).
Range compare
The execution timing of the range comparison is after the A/D conversion result is set in A/D data register
(ADTCD) when the A/D conversion is completed. Therefore, the range comparison result is reflected
(RCOCD2 to RCOCD0 bit, RCOOF bit, and RCINT bit) delaying 2 cycles in the peripheral clock from the
generation of the A/D conversion completion interrupt request.
When confirming it outside the range of the range comparison, the continuous detection measurement does
not clear to 0 times and continue the continuous detection even if the state of the range comparison result
changes from larger than the upper bound threshold into smaller than lower bound threshold.
When you want to initialize the continuous detection count of the range comparison result, please change to
enable setting (ADRCCS.RCOE="0" → "1") after the setting of the range comparison execution disable
while the A/D is not being requested.
About the continuous scan conversion that doesn't use the conversion
count specification of each channel
When two or more repeat modes (ADTCS.RPT="1") are set between the activation channels corresponding
to the same A/D converter unit, only certain one channel (channel with the highest priority level) will be
processed in the A/D activation arbitration of latter part. Therefore, please make the protection function
effective about those activation channels when the repeat mode is set with two or more activation channels.
When two or more repeat modes (ADTCS.RPT="1") are set between the activation channels corresponding
to the same A/D converter unit, the conversion of the activation channel with low priority is not executed if
the state of the data protection of the activation channel with high priority is released before converting the
activation channel with low priority. Therefore, the activation channel of low priority is not executed and
the scan conversion is not executed normally when the state of the data protection is released before the
MB91520 Series
MN705-00010-1v0-E
1920