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Enhanced Direct Memory Access (eDMA)
19-4
Freescale Semiconductor
•
The request is considered spurious and discarded, because the request is removed during arbitration
for next channel selection.
•
The channel is selected by arbitration and begins execution.
19.4
Memory Map/Register Definition
The eDMA’s programming model is partitioned into two regions: the first region defines a number of
registers providing control functions, while the second region corresponds to the local transfer control
descriptor memory.
Reading reserved bits in a register return the value of zero and writes to reserved bits in a register are
ignored. Reading or writing to a reserved memory location generates a bus error.
19.4.1
eDMA Control Register (EDMA_CR)
The EDMA_CR defines the basic operating configuration of the eDMA. Arbitration can be configured to
use a fixed-priority or a round-robin scheme. In fixed-priority arbitration, the highest priority channel
requesting service is selected to execute. The channel priority registers assign the priorities (see
Section 19.4.15, “eDMA Channel n Priority Registers (DCHPRIn)”
). In round-robin arbitration mode, the
channel priorities are ignored, and channels are cycled through without regard to priority.
Table 19-2. eDMA Controller Memory Map
Address
Register
Width
(bits)
Access
Reset Value
Section/Page
0xFC04_4000
eDMA Control Register (EDMA_CR)
32
R/W
0x0000_0000
0xFC04_4004
eDMA Error Status Register (EDMA_ES)
32
R
0x0000_0000
0xFC04_400E eDMA Enable Request Register (EDMA_ERQ)
16
R/W
0x0000
0xFC04_4016
eDMA Enable Error Interrupt Register (EDMA_EEI)
16
R/W
0x0000
0xFC04_4018
eDMA Set Enable Request (EDMA_SERQ)
8
W
0x00
0xFC04_4019
eDMA Clear Enable Request (EDMA_CERQ)
8
W
0x00
0xFC04_401A eDMA Set Enable Error Interrupt Register (EDMA_SEEI)
8
W
0x00
0xFC04_401B eDMA Clear Enable Error Interrupt Register (EDMA_CEEI)
8
W
0x00
0xFC04_401C eDMA Clear Interrupt Request Register (EDMA_CINT)
8
W
0x00
0xFC04_401D eDMA Clear Error Register (EDMA_CERR)
8
W
0x00
0xFC04_401E eDMA Set START Bit Register (EDMA_SSRT)
8
W
0x00
0xFC04_401F
eDMA Clear DONE Status Bit Register (EDMA_CDNE)
8
W
0x00
0xFC04_4026
eDMA Interrupt Request Register (EDMA_INT)
32
R/W
0x0000
0xFC04_402E eDMA Error Register (EDMA_ERR)
32
R/W
0x0000
0xFC04_4100
+ hex(
n
)
eDMA Channel
n
Priority Register (DCHPRI
n
)
for
n
= 0 – 15
8
R/W
See Section
0xFC04_5000
+ hex(32
n
)
Transfer Control Descriptor (TCD
n
)
for
n
= 0 – 15
256
R/W
See Section
Содержание MCF54455
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