MAC7200 datasheet(564/976 Pages) FREESCALE

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Functional Description

MAC7200 Microcontroller Family Reference Manual, Rev. 2

486

Freescale Semiconductor

27.4

Functional Description

This section provides a complete functional description of the DMA Mux. The primary purpose of the

DMA 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 system

boot code. However, if the procedure outlined in Section 27.7.5, “Enabling and Configuring Sources,” is

followed, the configuration of the DMA Mux may be changed during the normal operation of the system.

Functionally, the DMA Mux channels may be divided into two classes: Channels 0–7, which implement

the normal routing functionality plus periodic triggering capability, and channels 8–15, which implement

only the normal routing functionality.

27.4.1

DMA Channels 0-7

Besides the normal routing functionality, channels 0–7 of the DMA Mux provide a special periodic

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 generated by the

Periodic Interrupt Timer (PIT); as such, the configuration of the periodic triggering interval is done via

configuration registers in the PIT. Please refer to Chapter 26, “Periodic Interrupt Timer (PIT_RTI)” for

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