82801FB Datasheet, PDF (518/786 Pages) Intel Corporation – Intel I/O Controller Hub 6 (ICH6) Family

UHCI Controllers Registers
Bit
Description
Global Reset (GRESET) — R/W.
0 = This bit is reset by the software after a minimum of 10 ms has elapsed as specified in Chapter 7
of the USB Specification.
2 _{1 = Global Reset. The host controller sends the global reset signal on the USB and then resets all}
its logic, including the internal hub registers. The hub registers are reset to their power on state.
Chip Hardware Reset has the same effect as Global Reset (bit 2), except that the host
controller does not send the Global Reset on USB.
Host Controller Reset (HCRESET) — R/W. The effects of HCRESET on Hub registers are slightly
different from Chip Hardware Reset and Global USB Reset. The HCRESET affects bits [8,3:0] of the
Port Status and Control Register (PORTSC) of each port. HCRESET resets the state machines of
the host controller including the Connect/Disconnect state machine (one for each port). When the
Connect/Disconnect state machine is reset, the output that signals connect/disconnect are negated
to 0, effectively signaling a disconnect, even if a device is attached to the port. This virtual
disconnect causes the port to be disabled. This disconnect and disabling of the port causes bit 1
1 ^{(connect status change) and bit 3 (port enable/disable change) of the PORTSC (D29:F0/F1/F2/}
F3:BASE + 10h) to get set. The disconnect also causes bit 8 of PORTSC to reset. About 64 bit times
after HCRESET goes to 0, the connect and low-speed detect will take place, and bits 0 and 8 of the
PORTSC will change accordingly.
0 = Reset by the host controller when the reset process is complete.
1 = Reset. When this bit is set, the host controller module resets its internal timers, counters, state
machines, etc. to their initial value. Any transaction currently in progress on USB is immediately
terminated.
Run/Stop (RS) — R/W. When set to 1, the ICH6 proceeds with execution of the schedule. The ICH6
continues execution as long as this bit is set. When this bit is cleared, the ICH6 completes the
current transaction on the USB and then halts. The HC Halted bit in the status register indicates
when the host controller has finished the transaction and has entered the stopped state. The host
controller clears this bit when the following fatal errors occur: consistency check failure, PCI Bus
0 ^errors.
0 = Stop
1 = Run
NOTE: This bit should only be cleared if there are no active Transaction Descriptors in the
executable schedule or software will reset the host controller prior to setting this bit again.
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Intel^® I/O Controller Hub 6 (ICH6) Family Datasheet