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Universal Serial Bus Interface – On-The-Go Module
10-74
Freescale Semiconductor
10.5.4
Servicing Interrupts
The interrupt service routine must understand there are high frequency, low frequency, and error
operations to order accordingly.
10.5.4.1
High Frequency Interrupts
In particular, high frequency interrupts must be managed in the order below. The most important of these
is listed first because the DCD must acknowledge a setup buffer in the timeliest manner possible.
10.5.4.1.1
Low Frequency Interrupts
The low frequency events include the following interrupts. These interrupts can be managed in any order
because they do not occur often in comparison to the high-frequency interrupts.
Table 10-59. Error Descriptions
Overflow
Number of bytes received exceeded max. packet size or total buffer length.
Note:
This error also sets the halt bit in the dQH, and if there are dTDs remaining in the
linked list for the endpoint, those are not executed.
ISO Packet Error
CRC error on received ISO packet. Contents not guaranteed correct.
ISO Fulfillment Error
Host failed to complete the number of packets defined in the dQH mult field within the given
(micro)frame. For scheduled data delivery, DCD may need to readjust the data queue
because a fulfillment error causes the device controller to cease data transfers on the pipe
for one (micro)frame. During the dead (micro)frame, the device controller reports error on
the pipe and primes for the following frame.
Table 10-60. Interrupt Managing Order
Execution
Order
Interrupt
Action
1a
USB Interrupt
1
EPSETUPSR
1
It is likely multiple interrupts stack up on any call to the interrupt service routine and during interrupt service routine.
Copy contents of setup buffer and acknowledge setup packet (as indicated
in
Section 10.5.3.5, “Managing Queue Heads”
). Process setup packet
according to USB specification chapter 9 or application specific protocol.
1b
USB Interrupt
EPCOMPLETE
Manage completion of dTD as indicated in
2
SOF Interrupt
Action as deemed necessary by application. This interrupt may not have a
use in all applications.
Table 10-61. Low Frequency Interrupt Events
Interrupt
Action
Port Change
Change software state information.
Sleep Enable (Suspend)
Change software state information. Low power managing as
necessary.
Reset Received
Change software state information. Abort pending transfers.
Summary of Contents for MCF54455
Page 33: ...xxviii Freescale Semiconductor ...
Page 67: ...Freescale Semiconductor 1 ...
Page 125: ...Freescale Semiconductor 1 ...
Page 145: ...Enhanced Multiply Accumulate Unit EMAC 5 21 Freescale Semiconductor ...
Page 173: ...Cache 6 28 Freescale Semiconductor ...
Page 179: ...Static RAM SRAM 7 6 Freescale Semiconductor ...
Page 207: ...Power Management 9 16 Freescale Semiconductor ...
Page 323: ...Reset Controller Module 13 8 Freescale Semiconductor ...
Page 389: ...Pin Multiplexing and Control 16 44 Freescale Semiconductor ...
Page 575: ...PCI Bus Controller 22 58 Freescale Semiconductor ...
Page 600: ...Advanced Technology Attachment ATA Freescale Semiconductor 23 25 ...
Page 601: ...Freescale Semiconductor 1 ...
Page 842: ...I2 C Interface Freescale Semiconductor 33 16 ...
Page 843: ...Freescale Semiconductor 1 ...
Page 921: ...Revision History A 6 Freescale Semiconductor ...