K60P100M100SF2RM Datasheet, PDF (1290/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Functional Description
• recently plugged into a USB port, and
• drawing no more than 2.5 mA total system current from the USB bus.
There are many allowable precursors to this set of initial conditions. For example, the
device could have been powered down and subsequently powered up upon being plugged
into the USB bus. Alternatively, the device could have been in a low power state that was
exited due to the plugin event. Or, the device could have been operating in normal run
mode, powered by a separate supply or non-rechargable battery.
46.5.1.2 VBUS Contact Detection
Once the device is plugged into a USB port, the VBUS_detect system interrupt is
triggered. System software should do the following to initialize the module and start the
charger detection sequence:
1. Restore power if the module is powered-off.
2. Set the CONTROL[SR] bit to initiate a software reset.
3. Configure the USBDCD module: Program the CLOCK register and the timing
parameters as needed.
4. Set the CONTROL[IE] bit to enable interrupts (by default), or clear the bit if using a
software polling method.
5. Set the CONTROL[START] bit to start the charger detection sequence.
46.5.1.3 Data Pin Contact Detection
Because the detection sequence depends upon the state of the USB D+, the module must
ensure that the data pins have made contact. USB plugs and receptables are designed
such that when the plug is inserted into the receptable, the power pins make contact
before the data pins make contact. See the following figure.
1290
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc.