From: https://www.doczj.com/doc/1b17731645.html,
1. UTMI USB
2.0 Transceiver Macrocell Interace
defines an interface between two IP blocks: the USB Tran sceiver Macrocell (IP) and the USB Link layer (SIE). The UTM I interface provides functionality for USB peripherals only, not f or USB hosts or On-The-Go.
2. UTMI+
adds host and On-The-Go capabilities to the USB system.
UTMI+ incrementally adds new functionality and interface si gnals to the Link and PHY.
UL PI: UTMI+ Low
3. ULPI: UTMI+ Low Pin Interface
The ULPI specification reduces the Link to PHY interface t o 12 or 8 signals, with support for all the features needed by
USB peripherals, hosts, and OTG. The result is a package si ze as small as 32 pins or less, compared with 64 to 80 pins for UTMI+.
4. ULPI PHY Register Set
There are four main types of registers:
ID Registers These registers provide a unique identifier to the USB system. If necessary,system software can change b ehavior based on different PHY attachment. This is not genera lly needed because PHY capabilities are chosen at hardware design time.
Mode Registers These registers control how the PHY beh aves. Many signals from UTMI+ are changed only when the U SB is idle, so they are placed in registers that are accessed only when the ULPI bus is idle. Several new features have al so been introduced, including Carkit Mode.
Interrupt Registers These registers inform the Link of stat us changes in the PHY. Many signals in UTMI+ convey inform ation to the Link that is not timing critical. Those signals have been replaced with status bytes and interrupt signaling. Statu s information is sent only when the ULPI bus is idle.
Extra Registers Additional register space is provided for t wo reasons. Some addresses have been reserved for future u se, while other registers are available for vendorspecific use.