SDFM features include:
- Eight external pins per SDFM
module
- Four sigma-delta data
input pins per SDFM module (SD-Dx, where x = 1 to 4)
- Four sigma-delta clock
input pins per SDFM module (SD-Cx, where x = 1 to 4)
- Different configurable modulator
clock modes supported:
- Mode 0: Modulator clock
rate equals the modulator data rate.
- Four independent, configurable
secondary filter (comparator) units per SDFM module:
- Four different filter
type selection (Sinc1/Sinc2/SincFast/Sinc3) options available
- Ability to detect
over-value condition, under-value condition, and Threshold-crossing
conditions
- Two independent
Higher Threshold comparators (used to detect over-value
condition)
- Two independent
Lower Threshold comparators (used to detect under-value
condition)
- One independent
Threshold-Crossing comparator (used to measure duty
cycle/frequency with eCAP)
- OSR value for comparator
filter unit (COSR) programmable from 1 to 32
- Four independent configurable
primary filter (data filter) units per SDFM module:
- Four different filter
type selection (Sinc1/Sinc2/SincFast/Sinc3) options available
- OSR value for data filter
unit (DOSR) programmable from 1 to 256
- Ability to enable or
disable (or both) individual filter module
- Ability to synchronize
all four independent filters of an SDFM module by using the Main Filter
Enable (MFE) bit or by using PWM signals
- Data filter output can be
represented in either 16 bits or 32 bits.
- Data filter unit has a
programmable mode FIFO to reduce interrupt overhead. The FIFO has the following
features:
- The primary filter (data
filter) has a 16-deep x 32-bit FIFO.
- The FIFO can interrupt
the CPU after programmable number of data-ready events.
- FIFO Wait-for-Sync
feature: Ability to ignore data-ready events until the PWM
synchronization signal (SDSYNC) is received. Once the SDSYNC event is
received, the FIFO is populated on every data-ready event.
- Data filter output can be
represented in either 16 bits or 32 bits.
- PWMx.SOCA/SOCB can be configured
to serve as SDSYNC source on a per-data-filter-channel basis.
- PWMs can be used to generate a
modulator clock for sigma-delta modulators.
- Configurable Input Qualification available for both SD-Cx and
SD-Dx
- Ability to use one filter channel
clock (SD-C1) to provide clock to other filter clock channels.
- Configurable digital filter
available on comparator filter events to blank out comparator events caused by
spurious noise
Figure 6-65 shows the SDFM module block diagram.