Datasheet

 2010 - 2015 Microchip Technology Inc. DS00001692C-page 23
USB251xB/xBi
5.1.8 REGISTER 07H: CONFIGURATION DATA BYTE 2
5.1.9 REGISTER 08H: CONFIGURATION DATA BYTE 3
Bit Number Bit Name Description
7 DYNAMIC Dynamic Power Enable: controls the ability of the hub to automatically change
from self-powered to bus-powered operation if the local power source is
removed or unavailable. It can also go from bus-powered to self-powered
operation if the local power source is restored.
When dynamic power switching is enabled, the hub detects the availability of
a local power source by monitoring LOCAL_PWR. If the hub detects a change
in power source availability, the hub immediately disconnects and removes
power from all downstream devices. It also disconnects the upstream port.
The hub will then re-attach to the upstream port as either a bus-powered hub
(if local power is unavailable) or a self-powered hub (if local power is
available).
0 : no dynamic auto-switching
1 : dynamic auto-switching capable
6 rsvd
5:4 OC_TIMER Over Current Timer Delay:
00 : 0.1 ms
01 : 4.0 ms
10 : 8.0 ms
11 : 16.0 ms
3 COMPOUND Compound Device: indicates the hub is part of a compound device (see the
USB Specification for definition). The applicable port(s) must also be defined
as having a non-removable device.
Note: When configured via strapping options, declaring a port as non-
removable automatically causes the hub controller to report that it is
part of a compound device.
0 : no
1 : yes, the hub is part of a compound device
2:0 rsvd
Bit Number Bit Name Description
7:4 rsvd
3 PRTMAP_EN Port Mapping Enable: selects the method used by the hub to assign port
numbers and disable ports.
0 : standard mode
1 : port mapping mode
2:1 rsvd
0 STRING_EN Enables String Descriptor Support
0 : string support disabled
1 : string support enabled