Functional Description
1684
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Universal Serial Bus (USB) Controller
When the USB OTG controller B device has finished using the bus, the USB controller goes into
SUSPEND mode by setting the SUSPEND bit in the USBPOWER register. The A device detects this and
either terminates the session or reverts to host mode. If the A device is USB OTG controller, it generates
a Disconnect interrupt.
27.3.4 ULPI Interface
The ULPI PHY interface is a reduced pin-count interface conforms to the UTMI+ specification. The
reduction in pin count is achieved by allowing the relatively static UTMI+ signals to be accessed through
registers and by providing a bi-directional data bus both for the USB data and for accessing register data
on the ULPI transceiver. The PHY interface supports a 12-pin Single Data Rate (SDR) ULPI Standard.
27.3.4.1 Register Read
To execute a polled read, the steps are as follows:
1. Write the ULPIREGADDR register with the address of the read access.
2. Initiate a read access by setting the RDWR bit and the REGACC bit in the ULPIREGCTL register.
3. Poll the REGCMPLT bit in the ULPIREGCTL register to determine when the access is complete.
4. Clear the REGCMPLT bit and read the return data from the ULPIREGDATA register.
27.3.4.2 Register Write
To execute a polled write:
1. Write the ULPIREGADDR register with the address of the PHY register to be accessed.
2. Initiate the write to the register by setting the REGACC bit in the ULPREGCTL register.
3. Poll the REGCMPLT bit in the ULPIREGCTL register to determine when the access is complete.
4. Clear the REGCMPLT bit in the ULPIREGCTL register.
27.3.4.3 ULPI PHY Reset Operation
After power-up reset, the ULPI interface performs a write of 0x61 to the external ULPI PHY. This write
resets the ULPI PHY.
27.3.5 Link Power Management (LPM)
Link Power Management (LPM) allows the USB to be suspended and resumed by two basic methods.
The procedure in which the USB is suspended and resumed depends on whether the USB is operating as
a device or host and the method of suspend desired.
27.3.5.1 LPM Operation for USB as Device
In order for the USB, acting as a device, to be suspended by the host, the LPM feature must be enabled
by configuring the USB LPM Control (USBLPMCNTRL) register. The LPMEN field is used to enable and
support the LPM transactions and the TXLPM field is used to instruct the hardware that it is ready to
suspend and respond to the next LPM transaction with an ACK.
describes the response to an
LPM transaction by the USB device.
Table 27-1. USB Device LPM Transaction Response
TXLPM
LPMEN
Data Pending
(Data Resides
in the TX
FIFOs)
Response to
the Next LPM
Transaction
0
0x0
Don't care
Time-out
0
0x2
1
0x0
1
0x2