System overview
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SDL4/DVI Converter User's manual V1.12
3.3.2 General limitations/characteristics
•
USB 2.0 transfer is limited to 150 Mbit/s with SDL4.
•
If multiple USB devices are connected to the panel, it is important to note that only a certain number of
USB endpoints are available. If this number is exceeded, communication problems with the USB devices
may occur. This property is explained in detail below.
3.3.2.1 USB endpoint analysis
It is possible to analyze the number and type of endpoints on a particular USB device. Third-party USB analysis
tools can be used for this purpose.
The SDL4 connection has a limited number of USB IN and USB OUT endpoints. This can cause problems if multiple
USB devices are connected at the same time.
Endpoints
Devices
must be distinguished from
endpoints
:
A device can be considered a USB peripheral that connects to a host, such as a mouse, keyboard, camera, flash
drive or mass storage device such as a hard disk.
Endpoints can be considered as data sources or storage locations, i.e. buffers that cache data during a transaction.
This means that a USB device can have multiple endpoints. There is no direct relation between the number of
endpoints and the number of devices supported by a USB port.
Devices
SDL4 technology currently supports up to seven USB devices. Hubs are not counted since they are transparent
(not visible) from the user's perspective. They are not considered as a device, nor are they counted in relation
to endpoints.
The limitation concerning the maximum number of connected devices or maximum number of endpoints applies
as soon as one of the maximum values is reached. For example, if all endpoints are assigned (i.e. allocated) by
connecting two devices, no more devices are permitted to be connected (although the maximum of seven devices
has not yet been reached).
Hubs
SDL4 currently supports up to eight downstream ports per hub. This means that it is possible to identify all eight
ports on a given hub. By comparison, if SDL4 supported only four ports per hub, ports five to eight – on an eight-
port hub – would be switched off and therefore unusable.
If more than one hub is connected (e.g. if several hubs are linked together), the limit of eight ports per hub remains.
Determining the maximum available endpoints
A certain number of endpoints is available depending on the transfer rate of the devices used.
Endpoints
Transfer rate of the devices
IN
OUT
High speed
11
12
Full speed / Low speed
12
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