USB4604 datasheet(55/71 Pages) SMSC

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USB 2.0 HSIC Hi-Speed 4-Port Hub Controller

Datasheet

SMSC USB4604

Revision 1.0 (06-17-13)

DATASHEET

8.2

SOF Clock Output

The USB4604 provides an 8Khz clock output synchronized to the USB host SOFs. The SOF output is

generated from the previous SOF packet on the USB line. The device includes an internal free running

frame counter to generate internal start of frame and end of frame events. The internal counter is re-

synchronized every time a successful packet is received and decoded. The internal counter is

advanced to compensate for the packet decode time. If the incoming SOF jitters early or late, the jitter

will be visible in the next frame SOF output clock rising edge.

If one or two SOFs are missing, the SOF output will continue based on the internal frame counter. If

more than two SOF are missing, the SOF output signal will stop. The clock is guaranteed to stop in a

low state. When enabled or disabled, there will never be a short cycle.

Figure 8.2 SOF Output Timing

8.3

Flex Connect

This feature allows the upstream port to be swapped with downstream physical port 1. Only

downstream port 1 can be swapped physically. Using port remapping, any logical port (number

assignment) can be swapped with the upstream port (non-physical).

Flex Connect is enabled/disabled via two control bits in the Connect Configuration Register. The

FLEXCONNECT configuration bit switches the port, and EN_FLEX_MODE enables the mode.

8.3.1

Port Control

Once EN_FLEX_MODE bit is set, the functions of certain pins change, as outlined below.

If EN_FLEX_MODE is set and FLEXCONNECT is not set:

1. PRTPWR1 enters combined mode, becoming PRTPWR1/OCS1_N

2. OCS1_N becomes a don’t care

3. SUSPEND outputs ‘0’ to keep any upstream power controller off

If EN_FLEX_MODE is set and FLEXCONNECT is set:

1. The normal upstream VBUS pin becomes a don’t care

2. PRTPWR1 is forced to a ‘1’ in combined mode, keeping the port power on to the application

processor.

3. OCS1 becomes VBUS from the application processor through a GPIO

4. SUSPEND becomes PRTPWR1/OCS1_N for the port power controller for the connector port

Upstream HS USB

Internal frame

counter events

SOF (kHz)

SOF packet accepted

EOF1

EOF2

SOF

SOF packet accepted

EOF1

EOF2

SOF

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