GL850G データシートの表示（PDF） - Genesys Logic

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GL850G

USB 2.0 HUB Controller

Genesys Logic 

GL850G USB 2.0 Low-Power HUB Controller

5.1.10. TT (Transaction Translator)

TT implements the control logic defined in section 11.14 ~ 11.22 of USB specification Revision 2.0. TT

basically handles the unbalanced traffic speed between the USPORT (operating in HS) and DSPORTS

(operating in FS/LS) of hub. GL850G adopts the single TT architecture to provide the most cost effective

solution. Single TT shares the same buffer control module for each downstream port. GL852 adopts

multiple TT architecture to provide the most performance effective solution. Multiple TT provides control

logics for each downstream port respectively. Please refer to GL852 datasheet for more detailed

information.

5.1.11 REPEATER/TT routing logic

REPEATER and TT are the major traffic control machines in the USB 2.0 hub. Under situation that

USPORT and DSPORT are signaling in the same speed, REPEATER/TT routing logic switches the traffic

channel to the REPEATER. Under situation that USPORT is in the high speed signaling and DSPORT is in

the full/low speed signaling, REPEATER/TT routing logic switches the traffic channel to the TT.

5.1.11.1 Connected to 1.1 Host/Hub

If an USB 2.0 hub is connected to the downstream port of an USB 1.1 host/hub, it will operate in USB 1.1

mode. For an USB 1.1 hub, both upstream direction traffic and downstream direction traffic are passing

through REPEATER. That is, the REPEATER/TT routing logic will route the traffic channel to the

REPEATER.

USB1.1 HOST/HUB

Traffic channel

is routed to

REPEATER

REPEATER

USPORToperating

in FS signaling

TT

DSPORT operating

in FS/LS signaling

Figure 5.1 – Operating in USB 1.1 scheme

5.1.11.2 Connected to USB 2.0 Host/Hub

If an USB 2.0 hub is connected to an USB 2.0 host/hub, it will operate in USB 2.0 mode. The upstream port

signaling is in high speed with bandwidth of 480 Mbps under this environment. The traffic channel will

then be routed to the REPEATER when the device connected to the downstream port is signaling also in

high speed. On the other hand, the traffic channel will then be routed to TT when the device connected to

the downstream port is signaling in full/low speed.

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