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Enhanced Direct Memory Access (eDMA)
19-8
Freescale Semiconductor
19.4.3
eDMA Enable Request Register (EDMA_ERQ)
The EDMA_ERQ register provides a bit map for the 16 implemented channels to enable the request signal
for each channel. The state of any given channel enable is directly affected by writes to this register; it is
also affected by writes to the EDMA_SERQ and EDMA_CERQ. The EDMA_{S,C}ERQR are provided
so the request enable for a single channel can easily be modified without needing to perform a
read-modify-write sequence to the EDMA_ERQ.
DMA request input signals and this enable request flag must be asserted before a channel’s hardware
service request is accepted. The state of the eDMA enable request flag does not affect a channel service
request made explicitly through software or a linked channel request.
The assignments between the DMA requests from the peripherals to the channels of the eDMA are shown
in
Address: 0xFC04_400E (EDMA_ERQ)
Access: User read/write
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
R ERQ
15
ERQ
14
ERQ
13
ERQ
12
ERQ
11
ERQ
10
ERQ
9
ERQ
8
ERQ
7
ERQ
6
ERQ
5
ERQ
4
ERQ
3
ERQ
2
ERQ
1
ERQ
0
W
Reset
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Figure 19-5. eDMA Enable Request Register (EDMA_ERQ)
Table 19-5. EDMA_ERQ Field Descriptions
Field
Description
15–0
ERQ
n
Enable DMA Request
n.
0 The DMA request signal for channel
n
is disabled.
1 The DMA request signal for channel
n
is enabled.
Table 19-6. DMA Request Summary for eDMA
Channel
Source
Description
0
DREQ0
External DMA request 0
1
DREQ1
External DMA request 1
2
UISR0[FFULL/RXRDY]
UART0 Receive
3
UISR0[TXRDY]
UART0 Transmit
4
UISR1[FFULL/RXRDY]
UART1 Receive
5
UISR1[TXRDY]
UART1 Transmit
6
UISR2[FFULL/RXRDY]
UART2 Receive
7
UISR2[TXRDY]
UART2 Transmit
8
DTER0[CAP] or DTER0[REF] /
SSISR[RFF0]
Timer 0 / SSI0 Receive
1
9
DTER1[CAP] or DTER1[REF] /
SSISR[RFF1]
Timer 1 / SSI1 Receive
Содержание MCF54455
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Страница 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
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