Preliminary
Interrupt Support
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20.7.1.1 Subsystem Interrupts
The following interrupts are generated by the USB subsystem:
Table 20-27. Subsystem Interrupts
Interrupt
Description
rx_sop_starvation
Queue Manager cannot obtain a valid descriptor at SOP and has starvation status.
rx_mop_starvation
Queue Manager cannot obtain a valid descriptor during MOP and has starvation status.
pd_cmp_flag
When the packet is completed and the Packet Descriptor is pushed into the Queue Manager.
tx_pkt_cmp_0
USB0 Tx CPPI DMA Packet completion status
rx_pkt_cmp_0
USB0 Rx CPPI DMA Packet completion status
tx_pkt_cmp_1
USB1 Tx CPPI DMA Packet completion status
rx_pkt_cmp_1
USB1 Rx CPPI DMA Packet completion status
The pd_cmp_flag is only set when bit 31 of the original buffer length word (word 6) of a packet
descriptor (not buffer descriptor) has been set.
The USBSS QMGR outputs 60 packet completion signals for the four Tx/Rx CPPI DMA Packet
Completion Status interrupts as shown in
. The mapping of the packet completion signals is
shown in
. Therefore, each packet completion consists of the combination of the data from
the 15 individual packet completion signals. When one of the 15 packet completion signals was active
(level high) then an interrupt would be generated (if enabled).
Table 20-28. CPPI DMA Packet Completion Hardware Interrupt Groupings
Interrupt
CPPI DMA Packet Completion Grouping (EP)
Description
tx_pkt_cmp_0
1, 2, …, 15
USB0 Tx CPPI DMA Packet completion status
rx_pkt_cmp_0
1, 2, …, 15
USB0 Rx CPPI DMA Packet completion status
tx_pkt_cmp_1
1, 2, …, 15
USB1 Tx CPPI DMA Packet completion status
rx_pkt_cmp_1
1, 2, …, 15
USB1 Rx CPPI DMA Packet completion status
In order to control the frequency of the generated interrupts, interrupt pacing has been added to each of
the 60 individual packet completions. Each packet completion has its own 8-bit unsigned threshold.
Each threshold can range from 0 to 255. The packet descriptor for each of the packet completion
signals will have a differed bit. This bit will indicate whether the packet completion will be incremented
or not. If the count of the packet completion exceeds the threshold; then an interrupt will be generated.
This assumes that the packet completion is enabled. The thresholds for the 60 packet completions are
stored in one of the following registers: USBSS IRQ_DMA_THRESHOLD_ab_c. Where:
(a) Tx or Rx
(b) 0 or 1
(c) 0, 1, 2, or 3
The 60 DMA enables are stored in registers: USBSS IRQ_DMA_ENABLE_0 and USBSS
IRQ_DMA_ENABLE_1.
The individual packet completion count registers will be reset to zero when one of the below conditions
occurs:
•
Reset signal is active.
•
Packet completion threshold has been exceeded.
•
Packet completion count is equal to 255.
•
Frame count threshold has been exceeded.
•
Frame count is equal to 255.
1822
Universal Serial Bus (USB)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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