Since modes have been defined that allow the peripheral to send 8 bits of data back to the host over the data lines, it is possible for both the host and the peripheral to be driving the data lines at the same time. This can result in damage to the host port or the peripheral port or both. This would be very, very rare in normal operation but the following possiblilitys arise:

1. Since the host will always tri-state the data lines prior to asserting the signal telling the Peripheral that it is allowed to drive them, Host lockup should never result in a crash. Since each of the modes requires that the Peripheral signal
2. Hopefully the Peripheral will only actually drive the data bus during the short period of time required to reverse strobe the data into the PC. If the pc does not reverse ack the data due to lockup, a return to a forward mode that the peripheral did not see or other failure, the bus will not be driven by the Peripheral again.

See also:

• /techref/shorts.htm Protecting against short circuits+

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