Universal Serial Bus Interface
MCF5253 Reference Manual, Rev. 1
Freescale Semiconductor
24-147
24.11.6 Servicing Interrupts
The interrupt service routine must consider that there are high-frequency, low-frequency operations, and
error operations and order accordingly.
24.11.6.1 High-Frequency Interrupts
High frequency interrupts in particular should be handed 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.
24.11.6.2 Low-Frequency Interrupts
The low frequency events include the following interrupts. These interrupt can be handled in any order
since they don't occur often in comparison to the high-frequency interrupts.
24.11.6.3 Error Interrupts
Error interrupts will be least frequent and should be placed last in the interrupt service routine.
Table 24-90. Interrupt Handling Order
Execution
Order
Interrupt
Action
1a
USB Interrupt
1
ENDPTSETUPSTATUS
1
It is likely that multiple interrupts to stack up on any call to the Interrupt Service Routine AND during the Interrupt Service
Routine.
Copy contents of setup buffer and acknowledge setup packet (as indicated in
Section 24.11.4, “Managing Queue Heads
). Process setup packet according to USB
2.0 Chapter 9 or application specific protocol.
1b
USB Interrupt
ENDPTCOMPLETE
Handle completion of dTD as indicated in
Section 24.11.4, “Managing Queue Heads
.
2
SOF Interrupt
Action as deemed necessary by application. This interrupt may not have a use in all
applications.
Table 24-91. Low Frequency Interrupt Events
Interrupt
Action
Port Change
Change the software state information.
Sleep Enable (Suspend)
Change the software state information. Low power handling as
necessary.
Reset Received
Change the software state information. Abort pending transfers.
Table 24-92. Error Interrupt Events
Interrupt
Action
USB Error Interrupt This error is redundant because it combines USB Interrupt and an error status in the dTD. The DCD will
more aptly handle packet-level errors by checking dTD status field upon receipt of USB Interrupt
(w/ ENDPTCOMPLETE).
System Error
Unrecoverable error. Immediate Reset of core; free transfers buffers in progress and restart the DCD.
Summary of Contents for MCF5253
Page 1: ...Document Number MCF5253RM Rev 1 08 2008 MCF5253 Reference Manual...
Page 26: ...MCF5253 Reference Manual Rev 1 xxvi Freescale Semiconductor...
Page 32: ...MCF5253 Reference Manual Rev 1 xxxii Freescale Semiconductor...
Page 46: ...MCF5253 Introduction MCF5253 Reference Manual Rev 1 1 14 Freescale Semiconductor...
Page 62: ...Signal Description MCF5253 Reference Manual Rev 1 2 16 Freescale Semiconductor...
Page 98: ...Instruction Cache MCF5253 Reference Manual Rev 1 5 10 Freescale Semiconductor...
Page 104: ...Static RAM SRAM MCF5253 Reference Manual Rev 1 6 6 Freescale Semiconductor...
Page 128: ...Synchronous DRAM Controller Module MCF5253 Reference Manual Rev 1 7 24 Freescale Semiconductor...
Page 144: ...Bus Operation MCF5253 Reference Manual Rev 1 8 16 Freescale Semiconductor...
Page 176: ...System Integration Module SIM MCF5253 Reference Manual Rev 1 9 32 Freescale Semiconductor...
Page 198: ...Analog to Digital Converter ADC MCF5253 Reference Manual Rev 1 12 6 Freescale Semiconductor...
Page 246: ...DMA Controller MCF5253 Reference Manual Rev 1 14 18 Freescale Semiconductor...
Page 282: ...UART Modules MCF5253 Reference Manual Rev 1 15 36 Freescale Semiconductor...
Page 344: ...Audio Interface Module AIM MCF5253 Reference Manual Rev 1 17 46 Freescale Semiconductor...
Page 362: ...I2 C Modules MCF5253 Reference Manual Rev 1 18 18 Freescale Semiconductor...
Page 370: ...Boot ROM MCF5253 Reference Manual Rev 1 19 8 Freescale Semiconductor...