Chapter 19 DMA Channel Mux (DMA_MUX)
MPC5602P Microcontroller Reference Manual, Rev. 4
430
Freescale Semiconductor
19.5
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 19.6.2, “Enabling and configuring sources
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 that implement the
normal routing functionality plus periodic triggering capability, and channels that implement only the
normal routing functionality.
19.5.1
DMA channels with periodic triggering capability
Besides the normal routing functionality, the first four channels 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 30, “Periodic Interrupt Timer (PIT)
information on this topic.
NOTE
Because of the dynamic nature of the system (i.e., DMA channel priorities,
bus arbitration, interrupt service routine lengths, etc.), the number of clock
cycles between a trigger and the actual DMA transfer cannot be guaranteed.
25
—
ALWAYS requestors
DMA MUX Source #25
26
—
ALWAYS requestors
DMA MUX Source #26
27
—
ALWAYS requestors
DMA MUX Source #27
28
—
ALWAYS requestors
DMA MUX Source #28
29
—
ALWAYS requestors
DMA MUX Source #29
30
—
ALWAYS requestors
DMA MUX Source #30
Table 19-4. DMA channel mapping (continued)
DMA_CH_MUX
channel
Module
DMA requesting
module
DMA Mux input #