NXP Semiconductors MPC5644A, Reference Manual, Page: 1212 / 1735

Decimation Filter
MPC5644A Microcontroller Reference Manual, Rev. 6
1212 Freescale Semiconductor
26.5.11 Interrupts requests description
26.5.11.1 Block interrupt request
There are several interrupt request events that can be enabled using the module configuration register
DECFILTER_MCR. Basically, the interrupt request can be issued under any of the following conditions:
• when a word of input data is received
• when a word of output data is available
• when an error has occurred.
The input data flag IDF is set when a word of data is received from the CPU when in standalone mode, or
when a word of data is received in the PSI when it is not in standalone mode (normal mode). It is not used
to generate the read or write requests (as defined in
Section 26.5.11.2, Input buffer interrupt request ) when
DSEL = 0.
Output data is available and its flag (ODF) is set when the input data sample is processed by the filter and
the decimation counter matches the decimation rate value. It is not used to generate the read requests (as
defined in
Section 26.5.11.3, Output buffer interrupt request ) when DSEL = 0.
An error event in the decimation filter block is defined as one of these events:
• Overflow in the filter, flagged by OVF
• Overrun in the decimation filter input, flagged by IVR
• Overrun in the decimation filter output, flagged by OVR
• Overrun in enhanced debug monitor, flagged by DIVR
• Integrator overrun, flagged by SVR
• Integrator value exception, flagged by SSE
• Integrator count exception, flagged by SCE
An overflow occurs when the two’s-complement result value from the MAC accumulator is out of the
range of values that can be stored in tap register 4 (IIR) or in the output register.
An input overrun occurs when the input buffer is holding a word of input data and one more word of data
is received by the filter. See
Section 26.5.3.1, Input buffer overrun , for more details.
An output overrun occurs when a new word of data is sent to the output buffer but the previous word of
data has not been handled yet. See
Section 26.5.4.1, Output buffer overrun , for more details.
These flags can be set by the PSI events, however they are only cleared by
• the CPU, or
• by the soft reset command in the DECFILTER_MCR, or
•
by the clear flag fields in the DECFILTER_MSR
.
26.5.11.2 Input buffer interrupt request
This interrupt is enabled by the register IBIE in the DECFILTER_MCR and is asserted only when DSEL
= 0. This request is flagged in the DECFILTER_MSR by field IBIF.
In standalone and PSI output mixed modes, the input buffer interrupt request is asserted when the input
buffer is available to receive a conversion sample and DMA operation is not selected (DSEL = 0), meaning