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usb 的phy 协议发展历程
UTMI
- UTMI USB 2.0 Transceiver Macrocell Interace*
defines an interface between two IP blocks: the USB Transceiver Macrocell (IP) and the USB Link layer (SIE). The UTMI interface provides functionality for USB peripherals only, not for USB hosts or On-The-Go.
UTMI+
adds host and On-The-Go capabilities to the USB system.
UTMI+ incrementally adds new functionality and interface signals to the Link and PHY.
协议升级到UTMI+之后UTMI就被定义为UTMI LEVEL0
ULPI: UTMI+ Low Pin Interface**
The ULPI specification reduces the Link to PHY interface to 12 or 8 signals, with support for all the features needed by USB peripherals, hosts, and OTG. The result is a package size as small as 32 pins or less, compared with 64 to 80 pins for UTMI+.
如何区分
一般来说如果芯片的usb phy封装在芯片内，基本采用UTMI+的接口。不封装到芯片内的一般采用ULPI接口，这样可以降低pin的数量。