Decimation FilterMPC5644A Microcontroller Reference Manual, Rev. 61174 Freescale Semiconductor• Filter taps access for debug• Filter initialization (flush) and stabilization (prefill) commands• Timestamp support• Decimation controlled by an internal counter or from an on-chip independent trigger signal(triggered output result)• Integrator unit accumulates filter output values, signaled or absolute, with 32-bit resolution. Theintegrator can be controlled by software or hardware signals.• Cascade of 2 or more individual blocks to compose a more complex filter26.2.3 Modes of operationThis section describes the operation modes of the Decimation Filter. The modes are selected using theDECFILTER_MCR fields MDIS, FREN, FRZ, ISEL, MIXM, and CASCD (see Section 26.4.2.1,Decimation Filter Module Configuration Register (DECFILTER_MCR)”). The mode selection issummarized in Table 26-2.26.2.3.1 Normal modeThis is the default operational mode of the decimation filter block. It corresponds to the prefill/filteroperation with input data supplied through the PSI slave-bus interface (i.e. its input data is the ADCconversion result), with output going to the same PSI interface.26.2.3.2 Standalone modeStandalone mode differs from normal mode because the input data is not supplied by the master blockthrough the PSI slave-bus interface. In this case, the data is provided by the central processor using thedevice slave-bus interface or DMA interface signals. Once the data is filtered the decimated result isavailable in the Output Buffer register. The filter output is also consumed by a CPU or DMA masteringthe same device slave-bus interface. This operation mode can be used to debug the filter stability or todecimate data in System RAM.Table 26-2. Operation mode selectionMode MDIS FREN, FRZ ISEL MIXM CASCDNormal0(0, 0)or(0, 1)or(1, 0)0 000Standalone 1 0PSI Input Mixed 0 1PSI Output Mixed 1 1Cascade 0 or 1 0 01 or 10 or 11Freeze11 Freeze mode can also be activated from outside the Decimation Filter, depending on the MCU, ifFREN = 1.1, 1 X X XLow Power 1 X X X X
