Noise Generation; Figure 43. Dac Lfsr Register Calculation Algorithm; Figure 44. Dac Conversion (Sw Trigger Enabled) With Lfsr Wave Generation - ST STM32F410 Reference Manual

Digital-to-analog converter (DAC)
12.6

Noise generation

In order to generate a variable-amplitude pseudonoise, an LFSR (linear feedback shift
register) is available. DAC noise generation is selected by setting WAVEx[1:0] to "01". The
preloaded value in LFSR is 0xAAA. This register is updated three APB clock cycles after
each trigger event, following a specific calculation algorithm.
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.

Figure 44. DAC conversion (SW trigger enabled) with LFSR wave generation

Note: The DAC trigger must be enabled for noise generation by setting the TENx bit in the
DAC_CR register.
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Figure 43. DAC LFSR register calculation algorithm

RM0401 Rev 3
RM0401