Digital filter for sigma delta modulators (DFSDM) RM0351
604/1693 DocID024597 Rev 3
21.2 DFSDM main features
• Up to 8 multiplexed input digital serial channels:
– configurable SPI interface to connect various modulators
– configurable Manchester coded 1 wire interface support
– maximum input clock frequency up to 20 MHz (10 MHz for Manchester coded
stream)
– clock output for modulator(s): 0..20 MHz
• Alternative inputs from up to 8 internal digital parallel channels:
– inputs with up to 16 bit resolution
– internal sources: memory (CPU/DMA write) data streams
• Adjustable digital signal processing:
–Sinc
x
filter: filter order/type (1..5), oversampling ratio (up to 1..1024)
– integrator: oversampling ratio (1..256)
• Up to 24-bit output data resolution:
– right bit-shifter on final data (0..31 bits)
• Signed output data format
• Automatic data offset correction (offset stored in register by user)
• Continuous or single conversion
• Start-of-conversion synchronization with:
– software trigger
– internal timers
– external events
– start-of-conversion synchronously with first DFSDM (DFSDM0)
• Analog watchdog feature:
– low value and high value data threshold registers
– own configurable Sinc
x
digital filter (order = 1..3, oversampling ratio = 1..32)
– input from output data register or from one or more input digital serial channels
– continuous monitoring independently from standard conversion
• Short-circuit detector to detect saturated analog input values (bottom and top ranges):
– up to 8-bit counter to detect 1..256 consecutive 0’s or 1’s on input data stream
– monitoring continuously each channel (8 serial channel transceiver outputs)
• Break generation on analog watchdog event or short-circuit detector event
• Extremes detector:
– store minimum and maximum values of output data values
– refreshed by software
• DMA may be used to read the conversion data
• Interrupts: end of conversion, overrun, analog watchdog, short-circuit, channel clock
absence
• “regular” or “injected” conversions:
– “regular” conversions can be requested at any time or even in continuous mode
without having any impact on the timing of “injected” conversions
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