Figure 306. Sigma-Delta Adc External Modulator Interface - STMicroelectronics SPC572L series Reference Manual

Analog-to-digital converter (ADC) configuration
ADC. Currently, the AMC1203 external modulator is supported by the Sigma-Delta ADC. It
is possible that other external second order modulators with clock rates less than 10 MHz
and a compatible electrical interface (see SPC572Lx datasheet) could be supported.
The external modulator interface for the Sigma-Delta ADC on SPC572Lx is shown in
Figure 306.
CLKEXT[n]
CLKEXT[n]
CLKEXT[n]
BSEXT[n]
BSEXT[n]
BSEXT[n]
34.2.1.6.2 Clock/data inputs
Two external pins are required for the Sigma-Delta ADC to support an external modulator,
an input data pin BSEXT (bitstream data), and an input/output clock pin CLKEXT (bitstream
clock). When the external modulator is used, the clock and data inputs to the Sigma-Delta
ADC digital filters come from the CLKEXT and BSEXT pins, instead of the internal
modulator, as shown in
digital interface registers. The internal modulator is disabled. The CLKEXT and BSEXT
inputs are multiplexed on port input pins. The Sigma-Delta ADC has three sets of
CLKEXT/BSEXT pins, and selection of those pins is done in the SIUL2 MSCRs.
34.2.1.6.3 Clock output
SPC572Lx provides an option for an output clock from the device to the external modulator.
When providing an output clock, the SD_CLK from the CGM is connected to the CLKEXT
output pin. Both the input and output buffer of the CLKEXT pin must be enabled in the
corresponding SIUL2 MSCR, in order for both the external modulator and internal filters to
be clocked from the SD_CLK. This is shown in
698/2058

Figure 306. Sigma-Delta ADC external modulator interface

SIUL2 MSCR Register
I/O PAD
SIUL2 MSCR Register
I/O PAD
SIUL2 MSCR Register
I/O PAD
SIUL2 MSCR Register
I/O PAD
SIUL2 MSCR Register
I/O PAD
SIUL2 MSCR Register
I/O PAD
Figure 306. External modulator operation is enabled in the ADC
DocID027809 Rev 4
CGM
SD_CLK
Figure 306.
RM0400
SIUL2 MSCR Register
external clock
SD ADC
external data
SIUL2 MSCR Register