Renesas H8S/2100 Series, Hardware Manual

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Section 22 A/D Converter
Rev. 1.00 Apr. 28, 2008 Page 745 of 994
REJ09B0452-0100
22.7.8 Note on Activation of the A/D Converter by an External Trigger
When starting of the A/D converter by an external trigger* is in use, any of the following actions
(1. to 3.) may lead to a situation where stopping of the A/D converter is not possible.
Note:
*
External trigger: Conversion-start trigger from the peripheral modules (TMU and TPU)
1. Changing the value of the ADST bit in ADCSR from 0 to 1
2. Changing from the activation by external trigger setting to the external-trigger-disabled setting
3. Changing the scan-mode setting (changing the setting of the SCANE and ADSTCLR bits to
switch from continuous scan mode to single mode or one-cycle scan mode)
If any of the above points is applicable, please make settings in accord with the instructions below.
If 1. is applicable:
Do not set the ADST bit in ADCSR to 1.
If 2. or 3. is applicable:
Be sure to invalidate the external trigger input before changing the setting from activation by the
external trigger to disabling of the external trigger or changing the scan-mode setting (changing
the setting of the SCANE and ADSTCLR bits) while activation by the external trigger is in use.
Setting the TRGS1 and TRGS0 bits in ADCR according to the procedure overleaf invalidates the
external trigger input.
See figure 22.8 for details of the procedure in cases where 2. or 3. is applicable.