USB3370 datasheet(42/75 Pages) MICROCHIP

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USB3370

DS00001915B-page 42

 2012 - 2015 Microchip Technology Inc.

6.3.2.1

Disconnect Detection

A Hi-Speed host must detect a disconnect by sampling the transmitter outputs during the long EOP transmitted during

a SOF packet. The USB3370 only looks for a Hi-Speed disconnect during the long EOP where the period is long enough

for the disconnect reflection to return to the host PHY. When a Hi-Speed disconnect occurs, the USB3370 will return a

RXCMD and set the host disconnect bit in the USB Interrupt Status register.

When in FS or LS modes, the Link is expected to handle all disconnect detection.

6.3.2.2

Link Power Management (LPM) Token Receive

The USB3370 is fully capable of receiving the Extended PID in the LPM token. When the LPM 0000b PID is received,

this information is passed to the Link as a normal receive packet. If the Link chooses to enter LPM suspend, the proce-

dure detailed in Section 6.5.3 can be followed.

6.4

USB3370 Transmitter

The USB3370 ULPI transmitter fully supports HS, FS, and LS transmit operations. Figure 6-1 shows the Hi-Speed, Full

Speed, and Low Speed transmitter block controlled by ULPI Protocol Block. Encoding of the USB packet follows the bit-

stuffing and NRZI outlined in the USB 2.0 specification. Many of these functions are reused between the HS and FS/LS

transmitters. When using the USB3370, Table 5-1 should always be used as a guideline on how to configure for various

modes of operation. The transmitter decodes the inputs of XcvrSelect[1:0], TermSelect, OpMode[1:0], DpPulldown, and

DmPulldown

to determine what operation is expected. Users must strictly adhere to the modes of operation given in

Table 5-1.

Several important functions for a device and host are designed into the transmitter blocks.

The USB3370 transmitter will transmit a 32-bit long Hi-Speed sync before every Hi-Speed packet. In Full and Low Speed

modes a 8-bit sync is transmitted.

When the device or host needs to chirp for Hi-Speed port negotiation, the OpMode = 10 setting will turn off the bit-stuffing

and NRZI encoding in the transmitter. At the end of a chirp, the USB3370 OpMode register bits should be changed only

after the RXCMD linestate encoding indicates that the transmitter has completed transmitting. Should the opmode be

switched to normal bit-stuffing and NRZI encoding before the transmit pipeline is empty, the remaining data in the pipe-

line may be transmitted in an bit-stuff encoding format.

Please refer to the ULPI specification for a detailed discussion of USB reset and HS chirp.

6.4.1

USB3370 HOST FEATURES

The USB3370 can also support USB Host operation and includes the following features that are required for Host oper-

ation.

6.4.1.1

Hi-Speed Long EOP

When operating as a Hi-Speed host, the USB3370 will automatically generate a 40 bit long End of Packet (EOP) after

a SOF PID (A5h). The USB3370 determines when to send the 40-bit long EOP by decoding the ULPI TX CMD bits [3:0]

for the SOF. The 40-bit long EOP is only transmitted when the DpPulldown and DmPulldown bits in the OTG Control

In device mode, the USB3370 will not send a long EOP after a SOF PID.

6.4.1.2

Low Speed Keep-Alive

Low Speed keep alive is supported by the USB3370. When in Low Speed mode, the USB3370 will send out two Low

Speed bit times of SE0 when a SOF PID is received.

6.4.1.3

UTMI+ Level 3

Pre-amble is supported for UTMI+ Level 3 compatibility. When XcvrSelect is set to (11b) in host mode, (DpPulldown and

DmPulldown

both asserted) the USB3370 will pre-pend a Full Speed pre-amble before the Low Speed packet. Full

Speed rise and fall times are used in this mode. The pre-amble consists of the following: Full Speed sync, the encoded

pre-PID (C3h) and then Full Speed idle (DP=1 and DM = 0). A Low Speed packet follows with a sync, data and a LS EOP.

The USB3370 will only support UTMI+ Level 3 as a host. The USB3370 does not support UTMI+ Level 3 as a peripheral.

A UTMI+ Level 3 peripheral is an upstream hub port. The USB3370 will not decode a pre-amble packet intended for a

LS device when the USB3370 is configured as the upstream port of a FS hub, XcvrSelect = 11b, DpPulldown = 0b,

DmPulldown

=0b.

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