The occurrence of any error causes the eDMA engine to stop normal processing of the
active channel immediately (it goes to its error processing states and the transaction to the
system bus still has pipeline effect), and the appropriate channel bit in the eDMA error
register is asserted. At the same time, the details of the error condition are loaded into the
Error Status register (DMAx_ES). The major loop complete indicators, setting the
transfer control descriptor DONE flag and the possible assertion of an interrupt request,
are not affected when an error is detected. After the error status has been updated, the
eDMA engine continues operating by servicing the next appropriate channel. A channel
that experiences an error condition is not automatically disabled. If a channel is
terminated by an error and then issues another service request before the error is fixed,
that channel executes and terminates with the same error condition.
22.4.3 Channel preemption
Channel preemption is enabled on a per-channel basis by setting the DCHPRIn[ECP] bit.
Channel preemption allows the executing channel’s data transfers to temporarily suspend
in favor of starting a higher priority channel. After the preempting channel has completed
all its minor loop data transfers, the preempted channel is restored and resumes
execution. After the restored channel completes one read/write sequence, it is again
eligible for preemption. If any higher priority channel is requesting service, the restored
channel is suspended and the higher priority channel is serviced. Nested preemption, that
is, attempting to preempt a preempting channel, is not supported. After a preempting
channel begins execution, it cannot be preempted. Preemption is available only when
fixed arbitration is selected.
A channel’s ability to preempt another channel can be disabled by setting
DCHPRIn[DPA]. When a channel’s preempt ability is disabled, that channel cannot
suspend a lower priority channel’s data transfer, regardless of the lower priority channel’s
ECP setting. This allows for a pool of low priority, large data-moving channels to be
defined. These low priority channels can be configured to not preempt each other, thus
preventing a low priority channel from consuming the preempt slot normally available to
a true, high priority channel.
22.4.4 Performance
This section addresses the performance of the eDMA module, focusing on two separate
metrics:
Chapter 22 Enhanced Direct Memory Access (eDMA)
K22F Sub-Family Reference Manual , Rev. 3, 7/2014
Freescale Semiconductor, Inc.
481
Содержание MK22FN256VDC12
Страница 2: ...K22F Sub Family Reference Manual Rev 3 7 2014 2 Freescale Semiconductor Inc...
Страница 136: ...Human machine interfaces K22F Sub Family Reference Manual Rev 3 7 2014 136 Freescale Semiconductor Inc...
Страница 164: ...Module clocks K22F Sub Family Reference Manual Rev 3 7 2014 164 Freescale Semiconductor Inc...
Страница 246: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 246 Freescale Semiconductor Inc...
Страница 328: ...Kinetis Flashloader Status Error Codes K22F Sub Family Reference Manual Rev 3 7 2014 328 Freescale Semiconductor Inc...
Страница 360: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 360 Freescale Semiconductor Inc...
Страница 388: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 388 Freescale Semiconductor Inc...
Страница 402: ...Initialization application information K22F Sub Family Reference Manual Rev 3 7 2014 402 Freescale Semiconductor Inc...
Страница 500: ...Initialization application information K22F Sub Family Reference Manual Rev 3 7 2014 500 Freescale Semiconductor Inc...
Страница 670: ...Flash memory map for EzPort access K22F Sub Family Reference Manual Rev 3 7 2014 670 Freescale Semiconductor Inc...
Страница 680: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 680 Freescale Semiconductor Inc...
Страница 744: ...Application information K22F Sub Family Reference Manual Rev 3 7 2014 744 Freescale Semiconductor Inc...
Страница 784: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 784 Freescale Semiconductor Inc...
Страница 794: ...Initialization Application Information K22F Sub Family Reference Manual Rev 3 7 2014 794 Freescale Semiconductor Inc...
Страница 960: ...Example configuration for chained timers K22F Sub Family Reference Manual Rev 3 7 2014 960 Freescale Semiconductor Inc...
Страница 1036: ...Device mode IRC48 operation K22F Sub Family Reference Manual Rev 3 7 2014 1036 Freescale Semiconductor Inc...
Страница 1040: ...USB Voltage Regulator Module Signal Descriptions K22F Sub Family Reference Manual Rev 3 7 2014 1040 Freescale Semiconductor Inc...
Страница 1094: ...Initialization application information K22F Sub Family Reference Manual Rev 3 7 2014 1094 Freescale Semiconductor Inc...
Страница 1128: ...Initialization application information K22F Sub Family Reference Manual Rev 3 7 2014 1128 Freescale Semiconductor Inc...
Страница 1216: ...Application information K22F Sub Family Reference Manual Rev 3 7 2014 1216 Freescale Semiconductor Inc...
Страница 1298: ...Functional description K22F Sub Family Reference Manual Rev 3 7 2014 1298 Freescale Semiconductor Inc...
Страница 1312: ...K22F Sub Family Reference Manual Rev 3 7 2014 1312 Freescale Semiconductor Inc...