Atmel AT90PWM2, Руководство пользователя

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262
4317I–AVR–01/08
AT90PWM2/3/2B/3B
• Bit 2 – DALA: Digital to Analog Left Adjust
Set this bit to left adjust the DAC input data.
Clear it to right adjust the DAC input data.
The DALA bit affects the configuration of the DAC data registers. Changing this bit affects the
DAC output on the next DACH writing.
• Bit 1 – DAOE: Digital to Analog Output Enable bit
Set this bit to output the conversion result on D2A,
Clear it to use the DAC internally.
• Bit 0 – DAEN: Digital to Analog Enable bit
Set this bit to enable the DAC,
Clear it to disable the DAC.
22.4.2 Digital to Analog Converter input Register – DACH and DACL
DACH and DACL registers contain the value to be converted into analog voltage.
Writing the DACL register forbid the update of the input value until DACH has not been written
too. So the normal way to write a 10-bit value in the DAC register is firstly to write DACL the
DACH.
In order to work easily with only 8 bits, there is the possibility to left adjust the input value. Like
this it is sufficient to write DACH to update the DAC value.
22.4.2.1 DALA = 0
22.4.2.2 DALA = 1
1 0 0 Timer/Counter0 Overflow
1 0 1 Timer/Counter1 Compare Match B
1 1 0 Timer/Counter1 Overflow
1 1 1 Timer/Counter1 Capture Event
Table 22-1. DAC Auto Trigger source selection (Continued)
DATS2 DATS1 DATS0 Description
Bit 7 6 5 4 3 2 1 0
- - - - - - DAC9 DAC8 DACH
DAC7 DAC6 DAC5 DAC4 DAC3 DAC2 DAC1 DAC0 DACL
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0
Bit 7 6 5 4 3 2 1 0
DAC9 DAC8 DAC7 DAC6 DAC5 DAC4 DAC3 DAC2 DACH
DAC1 DAC0 - - - - - - DACL
Read/Write R/W R/W R/W R/W R/W R/W R/W R/W
R/W R/W R/W R/W R/W R/W R/W R/W
Initial Value 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0