Information

Universal Serial Bus Interface
MPC8308 PowerQUICC II Pro Processor Reference Manual, Rev. 1
13-148 Freescale Semiconductor
13.8.5.6 Device Error Matrix
Table 13-91 summarizes packet errors that are not automatically handled by the USB controller.
Notice that the device controller handles all errors on Bulk/Control/Interrupt Endpoints except for a data
buffer overflow. However, for ISO endpoints, errors packets are not retried and errors are tagged as
indicated. Table 13-92 provides the error descriptions.
13.8.6 Servicing Interrupts
The interrupt service routine must consider that there are high-frequency, low-frequency operations, and
error operations and order accordingly.
13.8.6.1 High-Frequency Interrupts
High frequency interrupts in particular should be handed in the order shown in Table 13-93. The most
important of these is listed first because the DCD must acknowledge a setup buffer in the timeliest manner
possible.
Table 13-91. Device Error Matrix
Error Direction
Packet
Type
Data
Buffer
Error Bit
Transaction
Error Bit
Overflow ** RX Any 1 0
ISO Packet Error RX ISO 0 1
ISO Fulfillment Error Both ISO 0 1
Table 13-92. 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. If there are dTDs remaining in the linked list for the endpoint,
they will not be executed.
ISO Packet
Error
CRC Error on received ISO packet. Contents not guaranteed to be 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 the DCD may need to readjust the data queue because a fulfillment error will cause
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 13-93. Interrupt Handling Order
Execution
Order
Interrupt Action
1a USB Interrupt
1
ENDPTSETUPSTATUS
Copy contents of setup buffer and acknowledge setup packet (as indicated in
Section 13.8.4, “Managing Queue Heads”). Process setup packet according to USB
2.0 Chapter 9 or application specific protocol.