USB3320 datasheet(40/70 Pages) MICROCHIP

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USB3320

DS00001792B-page 40

 2014-2015 Microchip Technology Inc.

6.2.4.1

High Speed Long EOP

When operating as a Hi-Speed host, the USB3320 will automatically generate a 40 bit long End of Packet (EOP) after

a SOF PID (A5h). The USB3320 determines when to send the 40-bit long EOP by decoding the ULPI TXD CMD bits

[3:0] for the SOF. The 40-bit long EOP is only transmitted when the DpPulldown and DmPulldown bits in the OTG Con-

trol register are asserted. The Hi-Speed 40-bit long EOP is used to detect a disconnect in high speed mode.

In device mode, the USB3320 will not send a long EOP after a SOF PID.

6.2.4.2

Low Speed Keep-Alive

Low speed keep alive is supported by the USB3320. When in Low speed (XcvrSelect = 10b in the Function Control

6.2.4.3

UTMI+ Level 3

Pre-amble is supported for UTMI+ Level 3 compatibility. When XcvrSelect = 11b in the Function Control register in host

mode (DpPulldown and DmPulldown both asserted), the USB3320 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 USB3320 will only support UTMI+ Level 3 as a host. The USB3320 does not support UTMI+ Level 3 as a peripheral.

A UTMI+ Level 3 peripheral is an upstream hub port. The USB3320 will not decode a pre-amble packet intended for a

LS device when the USB3320 is configured as the upstream port of a FS hub, XcvrSelect = 11b, DpPulldown = 0b,

DmPulldown

=0b.

6.2.4.4

Host Resume K

Resume K generation is supported by the USB3320. When the USB3320 exits the suspended (Low Power Mode), the

USB3320, when operating as a host, will transmit a K on DP/DM. The transmitters will end the K with SE0 for two Low

Speed bit times. If the USB3320 was operating in high speed mode before the suspend, the host must change to high

speed mode before the SE0 ends. SE0 is two low speed bit times which is about 1.2 us. For more details please see

sections 7.1.77 and 7.9 of the USB Specification.

In device mode, the resume K will not append an SE0, but release the bus to the correct idle state, depending upon the

operational mode as shown in Table 5-1.

The ULPI specification includes a detailed discussion of the resume sequence and the order of operations required. To

support Host start-up of less than 1mS the USB3320 implements the ULPI AutoResume bit in the Interface Control reg-

ister. The default AutoResume state is 0 and this bit should be enabled for Host applications.

6.2.4.5

No SYNC and EOP Generation (OpMode = 11)

UTMI+ defines OpMode = 11 where no sync and EOP generation occurs in Hi-Speed operation. This is an option to the

ULPI specification and not implemented in the USB3320.

6.2.4.6

Typical USB Transmit with ULPI

Figure 6-7 shows a typical USB transmit sequence. A transmit sequence starts by the Link sending a TXD CMD where

DATA[7:6]

= 01b, DATA[5:4] = 00b, and Data[3:0] = PID. The TX CMD with the PID is followed by transmit data.

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