Difference between Host and Device transceiver

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    Question: What is the difference between the host and the Device transceiver besides the low speed support?



    One difference is that you have to be able to determine the speed at which the device was connected. While the device is just connecting, the host has to know that the D- connect is the low speed and the D+ connect is a full speed. Along with that, for full speed, in order to determine if it is really a high speed device attaching, the host has to handle the chirp sequence from the host end of the handshake, not the device end. The host also has to have a circuit to detect disconnect. The device does not have the circuitry for this. The UTMI 1.05 spec on the Intel web site is a device end implementation. The UTMIplus specification covers disconnect signals, multiple pull-up detection, Host High Speed/Full Speed resume versus device resume and Host chirp versus peripheral chirp.