NXP Semiconductors K32 L2A Series, Reference Manual, Page: 1333 / 1379

USBx_CLK_RECOVER_INT_STATUS field descriptions
Field Description
7–5
Reserved
This field is reserved.
Should always be written as 0.
4
OVF_ERROR
Indicates that the USB clock recovery algorithm has detected that the frequency trim adjustment needed
for the FIRC output clock is outside the available TRIM_FINE adjustment range for the FIRC module.
0 No interrupt is reported
1 Unmasked interrupt has been generated
Reserved This field is reserved.
Should always be written as 0.
51.5 OTG and Host mode operation
The Host mode logic allows portable, mobile, and other devices using this SOC to
function as a USB Embedded Host (EH) Controller. The OTG logic adds an interface to
allow the OTG Host Negotiation and Session Request Protocols (HNP and SRP) to be
implemented in software.
Host mode is intended for use in handheld-portable devices to allow easy connection to
simple HID class devices such as printers and keyboards. It is not intended to perform the
functions of a full OHCI or UHCI compatible host controller found on PC motherboards.
Host mode allows bulk, isochronous, interrupt and control transfers. Bulk data transfers
are performed at nearly the full USB interface bandwidth. Support is provided for ISO
transfers, but the number of ISO streams that can be practically supported is affected by
the interrupt latency of the processor servicing the Token Done interrupts from the SIE.
Custom drivers must be written to support Host mode operation.
Setting the HOST_MODE_EN bit in the CTL register enables Host mode. The USB-FS
core can only operate as a peripheral device or in Host mode. It cannot operate in both
modes simultaneously. When HOST_MODE is enabled, only endpoint zero is used. All
other endpoints should be disabled by software.
51.6 Host Mode Operation Examples
The following sections illustrate the steps required to perform USB host functions using
the USB-FS core. For more information about these procedures, see the Universal Serial
Bus Specification, Revision 2.0
, "Chapter 9 USB Device Framework."
To enable host mode and discover a connected device:
Chapter 51 Universal Serial Bus Full Speed OTG Controller (USBFSOTG)
K32 L2A Reference Manual, Rev. 2, 01/2020
NXP Semiconductors 1333