Interrupts
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-21
The first priority parameter is the port, which changes each cycle. The second parameter is the
time to deadline, which determines the channel group. The last parameter is the channel number,
which gives higher priority to the lower channel number for channels in the same group with the
same priority. After each channel is serviced, all priorities are updated on a round-robin basis.
14.3.2.1 Issuing Interrupts
The EDF logic can issue a maskable interrupt request for each counter. The EDF issues its
interrupts on the error request line of the DMA controller. There is one source for EDF interrupts:
the threshold violation for each counter, as specified in the DMA EDF Status Register
(DMAEDFSTR) (see page 14-34). The EDF logic compares each counter value with the
threshold value. If a counter value equals the threshold value, EDF logic sets the corresponding
sticky bit in the pending register.
14.3.2.2 Counter Control
The EDF field in the source BD_ATTR of the channel defines the EDF logic behavior when
source BD_SIZE reached zero.
14.3.2.3 Clock Source to the Counters
All the counters share the same clock source. There are four clock sources: 3 external (to the
DMA) clock sources and the DMA clock divided by 16.
14.4
Interrupts
The DMA controller uses two types of interrupts: maskable and nonmaskable interrupts.
14.4.1 Maskable Interrupts
The DMA controller can issue one maskable interrupt per channel at the end of a buffer or end of
a transfer. For multi-dimension buffers, the interrupt may be issued on any of the dimensions. For
each maskable interrupt request, a bit in the DMA Status Register (DMASTR) indicates the
interrupt source. The interrupt mask is configured via bits in DMA Mask Register (DMAMR).
Maskable interrupts are output as 16 individual interrupts, one for each unidirectional destination
channel.
Most of the maskable interrupts are issued to request service or indicate that a transfer is
available. The exception is EDF threshold violation error interrupt. This interrupt can be masked
for each counter.
Содержание MSC8144E
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