LF1
RF1
LF2
RF2
CLK
FS
AXR4
LS1
RS1
LS2
RS2
AXR5
C1
LFE1
AXR6
C2
LFE2
AXEVTO
AREVTO
AXEVTE
AREVTE
AXEVTO
AREVTO
AXEVTE
AREVTE
AXEVTO
AREVTO
LF3
LS3
C3
Transmit
Receive
0
1
0
1
0
Preliminary
Architecture
www.ti.com
Here are some guidelines on using the different DMA events:
•
Either use AXEVT, or the combination of AXEVTO and AXEVTE, to service the McASP. Never use
all three at the same time. Similarly for receive, either use AREVT, or the combination of AREVTO
and AREVTE.
•
The McASP generates transmit DMA events independently from receive DMA events; therefore,
separate schemes can be used for transmit and receive DMA. For example, scenario 1 could be
used for the transmit data (AXEVT) and scenario 2 could be used for the receive data (AREVTO,
AREVTE), and conversely.
Note the difference between DMA event generation and the CPU interrupt generation. DMA events are
generated automatically upon data ready; whereas CPU interrupt generation needs to be enabled in the
XINTCTL/RINTCTL register.
In
, scenario 2, each transmit DMA request is for data in the next time slot, while each
receive DMA request is for data in the previous time slot. For example,
shows a circled
AXEVTE event for an even time slot transmit DMA request. The transmitter always requests a DMA
transfer for data it will need to transmit during the next time slot. So, in this example, the circled event
AXEVTE is a request for data for samples LF2, LS2, and C2.
On the other hand, the circled AREVTE event is an even time slot receive DMA request. The receiver
always requests a DMA transfer for data it received during the previous time slot. In this example, the
circled event AREVTE is a request for samples LF1, LS1, and C1.
Figure 10-37. DMA Events in an Audio Example
10.2.13 Power Management
The McASP can be placed in reduced power modes to conserve power during periods of low activity.
10.2.14 Emulation Considerations
NOTE:
The receive buffer registers (RBUFn) and transmit buffer registers (XBUFn) should not
be accessed by the emulator when the McASP is running. Such an access will cause the
RRDY/XRDY bit in the serializer control register n (SRCTLn) to be updated.
The McASP does not support the emulation suspend.
1066
Multichannel Audio Serial Port (McASP)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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