307013-003 Datasheet, PDF (203/848 Pages) Intel Corporation – Intel I/O Controller Hub 7

Functional Description
5.19.6.2
Serial Bus Babble
When a device transmits on the USB for a time greater than its assigned Max Length, it
is said to be babbling. Since isochrony can be destroyed by a babbling device, this error
results in the Active bit in the TD being cleared to 0 and the Stalled and Babble bits
being set to 1. The C_ERR field is not decremented for a babble. The USB Error
Interrupt bit in the HC Status register is set to 1 at the end of the frame. A hardware
interrupt is signaled to the system.
If an EOF babble was caused by the ICH7 (due to incorrect schedule for instance), the
ICH7 forces a bit stuff error followed by an EOP and the start of the next frame.
Stalled
This event indicates that a device/endpoint returned a STALL handshake during a
transaction or that the transaction ended in an error condition. The TDs Stalled bit is
set and the Active bit is cleared. Reception of a STALL does not decrement the error
counter. A hardware interrupt is signaled to the system.
Data Buffer Error
This event indicates that an overrun of incoming data or a under-run of outgoing data
has occurred for this transaction. This would generally be caused by the ICH7 not being
able to access required data buffers in memory within necessary latency requirements.
Either of these conditions causes the C_ERR field of the TD to be decremented.
When C_ERR decrements to 0, the Active bit in the TD is cleared, the Stalled bit is set,
the USB Error Interrupt bit in the HC Status register is set to 1 at the end of the frame
and a hardware interrupt is signaled to the system.
Bit Stuff Error
A bit stuff error results from the detection of a sequence of more that six 1s in a row
within the incoming data stream. This causes the C_ERR field of the TD to be
decremented. When the C_ERR field decrements to 0, the Active bit in the TD is cleared
to 0, the Stalled bit is set to 1, the USB Error Interrupt bit in the HC Status register is
set to 1 at the end of the frame and a hardware interrupt is signaled to the system.
Non-Transaction Based Interrupts
If an ICH7 process error or system error occur, the ICH7 halts and immediately issues a
hardware interrupt to the system.
Resume Received
This event indicates that the ICH7 received a RESUME signal from a device on the USB
bus during a global suspend. If this interrupt is enabled in the Interrupt Enable register,
a hardware interrupt is signaled to the system allowing the USB to be brought out of
the suspend state and returned to normal operation.
ICH7 Process Error
The HC monitors certain critical fields during operation to ensure that it does not
process corrupted data structures. These include checking for a valid PID and verifying
that the MaxLength field is less than 1280. If it detects a condition that would indicate
that it is processing corrupted data structures, it immediately halts processing, sets the
HC Process Error bit in the HC Status register and signals a hardware interrupt to the
system.
This interrupt cannot be disabled through the Interrupt Enable register.
Intel ^® ICH7 Family Datasheet
203