at90pwm81-16se ATMEL Corporation, at90pwm81-16se Datasheet - Page 230

• Manufacturer Part Number: at90pwm81-16se
• Description: 8-bit Avr Microcontroller With 8k Bytes In- System Programmable Flash
• Manufacturer: ATMEL Corporation

To work with the 10-bit DAC, two registers have to be updated. In order to avoid intermediate value, the
DAC input values which are really converted into analog signal are buffering into unreachable registers.
In normal mode, the update of the shadow register is done when the register DACH is written.
In case DAATE bit is set, the DAC input values will be updated on the trigger event selected through
DATS bits.
In order to avoid wrong DAC input values, the update can only be done after having written respectively
DACL and DACH registers. It is possible to work on 8-bit configuration by only writing the DACH value.
In this case, update is done each trigger event.
In case DAATE bit is cleared, the DAC is in an automatic update mode. Writing the DACH register auto-
matically update the DAC input values with the DACH and DACL register values.
It means that whatever is the configuration of the DAATE bit, changing the DACL register has no effect
on the DAC output until the DACH register has also been updated. So, to work with 10 bits, DACL must
be written first before DACH. To work with 8-bit configuration, writing DACH allows the update of the
DAC.
AT90PWM81
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7734M–AVR–03/10