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Functional Description
22.3.13.6 Multiple Interrupts
This only applies to interrupts and not to DMA requests. The following terms are defined:
• Active Interrupt Request: a flag in RSTAT or XSTAT is set and the interrupt is enabled in RINTCTL
or XINTCTL.
• Outstanding Interrupt Request: An interrupt request has been issued on one of the McASP
transmit/receive interrupt ports, but that request has not yet been serviced.
• Serviced: The CPU writes to RSTAT or XSTAT to clear one or more of the active interrupt request
flags.
The first interrupt request to become active for the transmitter with the interrupt flag set in XSTAT and the
interrupt enabled in XINTCTL generates a request on the McASP transmit interrupt port AXINT.
If more than one interrupt request becomes active in the same cycle, a single interrupt request is
generated on the McASP transmit interrupt port. Subsequent interrupt requests that become active while
the first interrupt request is outstanding do not immediately generate a new request pulse on the McASP
transmit interrupt port.
The transmit interrupt is serviced with the CPU writing to XSTAT. If any interrupt requests are active after
the write, a new request is generated on the McASP transmit interrupt port.
The receiver operates in a similar way, but using RSTAT, RINTCTL, and the McASP receive interrupt port
ARINT.
One outstanding interrupt request is allowed on each port, so a transmit and a receive interrupt request
may both be outstanding at the same time.
22.3.14 EDMA Event Support
22.3.14.1 EDMA Events
There are 6 EDMA events.
22.3.14.2 Using the DMA for McASP Servicing
The most typical scenario is to use the DMA to service the McASP through the data port, although the
DMA can also service the McASP through the configuration bus. Two possibilities exist for using the DMA
events to service the McASP:
1. Use AXEVT/AREVT: Triggered upon each XDATA/RDATA transition from 0 to 1.
2. Use AXEVTO/AREVTO and AXEVTE/AREVTE: Alternating AXEVT/AREVT events for odd/even slots.
Upon AXEVT/AREVT, AXEVTO/AREVTO is triggered if the event is for an odd channel, and
AXEVTE/AREVTE is triggered if the event is for an even channel.
NOTE: Check the device-specific data manual to see if AXEVTO/AREVTO and AXEVTE/AREVTE
are supported. These are optional.
Figure 22-36 and Figure 22-37 show an example audio system with six audio channels (LF, RF, LS, RS,
C, and LFE) transmitted from three AXRn pins on the McASP. Figure 22-36 and Figure 22-37 show when
events AXEVT, AXEVTO, and AXEVTE are triggered. Figure 22-36 and Figure 22-37 also apply for the
receive audio channels and show when events AREVT, AREVTO, and AREVTE are triggered.
You can either use the DMA to service the McASP upon events AXEVT and AREVT (Figure 22-36) or
upon events AXEVTO, AREVTO, AXEVTE, and AREVTE (Figure 22-37).
3823
SPRUH73H–October 2011–Revised April 2013 Multichannel Audio Serial Port (McASP)
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