Chapter 18 Enhanced Direct Memory Access (eDMA)
MPC5602P Microcontroller Reference Manual, Rev. 4
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Freescale Semiconductor
18.7.6.2
Active channel TCD reads
the eDMA reads the true TCD.SADDR, TCD.DADDR, and TCD.NBYTES values if read while a channel
is executing. The true values of the SADDR, DADDR, and NBYTES are the values the eDMA engine is
currently using in its internal register file and not the values in the TCD local memory for that channel.
The addresses (SADDR and DADDR) and NBYTES (decrements to zero as the transfer progresses) can
give an indication of the progress of the transfer. All other values are read back from the TCD local
memory.
18.7.6.3
Preemption status
Preemption is only available when fixed arbitration is selected for both group and channel arbitration
modes. A preempt-able situation is one in which a preempt-enabled channel is running and a higher
priority request becomes active. When the eDMA engine is not operating in fixed group, fixed channel
arbitration mode, the determination of the relative priority of the actively running and the outstanding
requests become undefined. Channel and/or group priorities are treated as equal (or more exactly,
constantly rotating) when round-robin arbitration mode is selected.
The TCD.ACTIVE bit for the preempted channel remains asserted throughout the preemption. The
preempted channel is temporarily suspended while the preempting channel executes one iteration of the
major loop. Two TCD.ACTIVE bits set at the same time in the overall TCD map indicates a higher priority
channel is actively preempting a lower priority channel.
18.7.7
Channel linking
Channel linking (or chaining) is a mechanism where one channel sets the TCD.START bit of another
channel (or itself) thus initiating a service request for that channel. This operation is automatically
performed by the eDMA engine at the conclusion of the major or minor loop when properly enabled.
The minor loop channel linking occurs at the completion of the minor loop (or one iteration of the major
loop). The TCD.CITER.E_LINK field determines whether a minor loop link is requested. When enabled,
the channel link is made after each iteration of the minor loop except for the last.
When the major loop is exhausted, only the major loop channel link fields are used to determine whether
to make a channel link. For example, with the initial fields of:
TCD.CITER.E_LINK = 1
TCD.CITER.LINKCH = 0xC
TCD.CITER value = 0x4
TCD.MAJOR.E_LINK = 1
TCD.MAJOR.LINKCH = 0x7
channel linking executes as:
1. Minor loop done
set channel 12 TCD.START bit
2. Minor loop done
set channel 12 TCD.START bit
3. Minor loop done
set channel 12 TCD.START bit
4. Minor loop done, major loop done
set channel 7 TCD.START bit
Содержание SAFE ASSURE Qorivva MPC5601P
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Страница 62: ...Chapter 2 MPC5602P Memory Map MPC5602P Microcontroller Reference Manual Rev 4 62 Freescale Semiconductor ...
Страница 104: ...Chapter 4 Clock Description MPC5602P Microcontroller Reference Manual Rev 4 104 Freescale Semiconductor ...
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Страница 272: ...Chapter 12 e200z0 and e200z0h Core MPC5602P Microcontroller Reference Manual Rev 4 272 Freescale Semiconductor ...
Страница 280: ...Chapter 14 Crossbar Switch XBAR MPC5602P Microcontroller Reference Manual Rev 4 280 Freescale Semiconductor ...
Страница 306: ...Chapter 16 Internal Static RAM SRAM MPC5602P Microcontroller Reference Manual Rev 4 306 Freescale Semiconductor ...
Страница 380: ...Chapter 17 Flash Memory MPC5602P Microcontroller Reference Manual Rev 4 380 Freescale Semiconductor ...
Страница 532: ...Chapter 21 LIN Controller LINFlex MPC5602P Microcontroller Reference Manual Rev 4 532 Freescale Semiconductor ...
Страница 578: ...Chapter 22 FlexCAN MPC5602P Microcontroller Reference Manual Rev 4 578 Freescale Semiconductor ...
Страница 708: ...Chapter 25 FlexPWM MPC5602P Microcontroller Reference Manual Rev 4 708 Freescale Semiconductor ...
Страница 742: ...Chapter 26 eTimer MPC5602P Microcontroller Reference Manual Rev 4 742 Freescale Semiconductor ...
Страница 760: ...Chapter 27 Functional Safety MPC5602P Microcontroller Reference Manual Rev 4 760 Freescale Semiconductor ...
Страница 782: ...Chapter 28 Fault Collection Unit FCU MPC5602P Microcontroller Reference Manual Rev 4 782 Freescale Semiconductor ...
Страница 788: ...Chapter 29 Wakeup Unit WKPU MPC5602P Microcontroller Reference Manual Rev 4 788 Freescale Semiconductor ...
Страница 798: ...Chapter 30 Periodic Interrupt Timer PIT MPC5602P Microcontroller Reference Manual Rev 4 798 Freescale Semiconductor ...
Страница 816: ...Chapter 32 Cyclic Redundancy Check CRC MPC5602P Microcontroller Reference Manual Rev 4 816 Freescale Semiconductor ...
Страница 848: ...Chapter 33 Boot Assist Module BAM MPC5602P Microcontroller Reference Manual Rev 4 848 Freescale Semiconductor ...
Страница 930: ...Chapter 36 Nexus Development Interface NDI MPC5602P Microcontroller Reference Manual Rev 4 930 Freescale Semiconductor ...