K60P100M100SF2RM Datasheet, PDF (1296/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
46.5.1.6 Charger Detection Sequence Timeout
The maximum time to connect allowed under the USB Battery Charging Specification,
v1.1 is one second. If the Unit Connection Timer reaches the one second limit and the
sequence is still running (indicated by the STATUS[ACTIVE] bit still being set), the
module does the following:
• Updates the STATUS register to reflect that a timeout error has occured. (See Table
46-18 for field values.)
• Sets the CONTROL[IF] bit.
• Generates an interrupt if enabled (the CONTROL[IE] bit is set).
• The detection sequence continues until explicitly halted by software setting the
CONTROL[SR] bit.
• The Unit Connection Timer continues counting. See the description of the TIMER0
Register.
At this point, control has been passed to system software via the interrupt, which has two
options: ignore the interrupt and allow more time for the sequence to complete, or halt the
sequence. To halt the sequence, software should:
1. Read the STATUS register.
2. Set the CONTROL[IACK] bit to acknowledge the interrupt.
3. Set the CONTROL[SR] bit to issue a software reset to the module.
4. Disable the module.
This timeout function is also useful in case software does not realize that the user
unplugged the USB device from the USB port during the charger detection sequence. If
the interrupt occurs but the V_{BUS_DETECT} input is low, software can disable and reset the
module.
System software might allow the sequence to run past the timeout interrupt under these
conditions:
1. the USB Battery Charging Spec is amended to allow more time. In this case,
software should poll the T_UNITCON register field (see the description of the TIMER0
Register) periodically to track elapsed time after 1s; or
2. for debug purposes.
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K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.