ST7LITE20F2 datasheet(161/166 Pages) STMICROELECTRONICS

161 / 166 page

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Important notes

Doc ID 8349 Rev 5

161/166

Important notes

16.1

Execution of BTJX instruction

When testing the address $FF with the "BTJT" or "BTJF" instructions, the CPU may perform

an incorrect operation when the relative jump is negative and performs an address page

change.

To avoid this issue, including when using a C compiler, it is recommended to never use

address $00FF as a variable (using the linker parameter for example).

16.2

ADC conversion spurious results

Spurious conversions occur with a rate lower than 50 per million. Such conversions happen

when the measured voltage is just between 2 consecutive digital values.

Workaround

A software filter should be implemented to remove erratic conversion results whenever they

may cause unwanted consequences.

16.3

A/D converter accuracy for first conversion

When the ADC is enabled after being powered down (for example when waking up from

HALT, ACTIVE-HALT or setting the ADON bit in the ADCCSR register), the first conversion

(8-bit or 10-bit) accuracy does not meet the accuracy specified in the datasheet.

Workaround

In order to have the accuracy specified in the datasheet, the first conversion after a ADC

switch-on has to be ignored.

16.4

Negative injection impact on ADC accuracy

Injecting a negative current on an analog input pins significantly reduces the accuracy of the

AD Converter. Whenever necessary, the negative injection should be prevented by the

addition of a Schottky diode between the concerned I/Os and ground.

Injecting a negative current on digital input pins degrades ADC accuracy especially if

performed on a pin close to ADC channel in use.

16.5

Clearing active interrupts outside interrupt routine

When an active interrupt request occurs at the same time as the related flag or interrupt

mask is being cleared, the CC register may be corrupted.

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