Figure 68. Dac Lfsr Register Calculation Algorithm; Figure 69. Dac Conversion (Sw Trigger Enabled) With Lfsr Wave Generation - ST STM32F405 Reference Manual

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The LFSR value, that may be masked partially or totally by means of the MAMPx[3:0] bits in

the DAC_CR register, is added up to the DAC_DHRx contents without overflow and this

value is then stored into the DAC_DORx register.

If LFSR is 0x0000, a '1 is injected into it (antilock-up mechanism).

It is possible to reset LFSR wave generation by resetting the WAVEx[1:0] bits.

The DAC trigger must be enabled for noise generation by setting the TENx bit in the

DAC_CR register.

Triangle-wave generation

It is possible to add a small-amplitude triangular waveform on a DC or slowly varying signal.

DAC triangle-wave generation is selected by setting WAVEx[1:0] to "10". The amplitude is

configured through the MAMPx[3:0] bits in the DAC_CR register. An internal triangle counter

is incremented three APB1 clock cycles after each trigger event. The value of this counter is

then added to the DAC_DHRx register without overflow and the sum is stored into the

DAC_DORx register. The triangle counter is incremented as long as it is less than the

maximum amplitude defined by the MAMPx[3:0] bits. Once the configured amplitude is

reached, the counter is decremented down to 0, then incremented again and so on.

Figure 68. DAC LFSR register calculation algorithm

RM0090 Rev 18

Digital-to-analog converter (DAC)

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