DMA Channel Mux (DMACHMUX)MPC5606S Microcontroller Reference Manual, Rev. 7454 Freescale Semiconductor13.4 Functional descriptionThis section provides a functional description of the DMA channel mux. The primary purpose of the DMAchannel mux is to provide flexibility in the system’s use of the available DMA channels. As such,configuration of the DMA Mux is intended to be a static procedure done during execution of the systemboot code. However, if the procedure outlined in Section 13.5.2, Enabling and configuring sources, isfollowed, the configuration of the DMA channel mux may be changed during the normal operation of thesystem.Functionally, the DMA channel mux channels may be divided into two classes: channels that implementthe normal routing functionality plus periodic triggering capability, and channels that implement only thenormal routing functionality.13.4.1 DMA channels with periodic triggering capabilityBesides the normal routing functionality, the first four channels of the DMA Mux provide a specialperiodic triggering capability that can be used to provide an automatic mechanism to transmit bytes,frames, or packets at fixed intervals without the need for processor intervention. The trigger is generatedby the Periodic Interrupt Timer (PIT); as such, the configuration of the periodic triggering interval is donevia configuration registers in the PIT. Please refer to Chapter 27, Periodic Interrupt Timer (PIT), for moreinformation on this topic.Table 13-5 shows the mapping of PIT channels to DMA channels for triggering.ALWAYS requestors 58ALWAYS requestors 59ALWAYS requestors 60ALWAYS requestors 61ALWAYS requestors 62ALWAYS requestors 631 Configuring a DMA channel to select source 0 or any reserved sources will disable that DMAchannel.Table 13-5. PIT-DMA channel mappingPIT channel number DMACHMUX channel numberfor triggering0 01 12 23 3Table 13-4. DMACHMUX request assignments (continued)DMA requesting module DMACHMUX source number(ipd_ref_peripher[Nperiphs :1])
