Information

Note
Software must always initiate a software reset before starting
the sequence to ensure the module is in a known state.
41.6 Initialization information
This module has been designed for minimal configuration while retaining significant
programmability. The CLOCK register needs to be initialized to the actual system clock
frequency, unless the default value already matches the system requirements.
The other registers generally do not need to be modified, because they default to values
that comply with the USB Battery Charging Specification v1.1. However, several timing
parameters can be changed for a great deal of flexibility if a particular system requires it.
All module configuration must occur before initiating the charger detection sequence.
Configuration changes made after setting CONTROL[START] result in undefined
behavior.
41.7 Application information
This section provides application information.
41.7.1 External pullups
Any external pullups applied to the USB D+ or D- data lines must be capable of being
disabled to prevent incorrect pullup values or incorrect operation of the USB subsystem.
41.7.2 Dead or weak battery
According to the USB Battery Charging Specification v1.1, a USB device with a dead,
weak, or missing battery that is attached to a charging port can remain attached
indefinitely drawing up to 1.5A, until the battery is charged to the point that the USB
device can connect.
The USBDCD module is compatible with systems that do not check the strength of the
battery. Therefore, this module assumes that the battery is good, so the USB device must
immediately connect to the USB bus by pulling the D+ line high after the USBDCD
module has determined that the device is attached to a charging port.
Initialization information
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
950 Freescale Semiconductor, Inc.