PIIX3 datasheet(81/122 Pages) INTEL

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82371FB (PIIX) AND 82371SB (PIIX3)

Bit

Description

Software Debug (SWDBG). 1=Debug mode. 0=Normal Mode. In SW Debug mode, the Host

Controller clears the Run/Stop bit after the completion of each USB transaction. The next

transaction is executed when software sets the Run/Stop bit back to 1. The SWDBG bit must

only be manipulated when the controller is in the stopped state. This can be determined by

checking the HCHalted bit in the USBSTS register.

Force Global Resume (FGR). 1=Host Controller sends the Global Resume signal on the

USB. Software sets this bit to 0 after 20 ms has elapsed to stop sending the Global Resume

signal. At that time all USB devices should be ready for bus activity. The Host Controller sets

this bit to 1 when a resume event (connect, disconnect, or K-state) is detected while in global

suspend mode. Software resets this bit to 0 to end Global Resume signaling. The 1 to 0

transition causes the port to send a low speed EOP signal. This bit remains a 1 until the EOP

has completed.

Enter Global Suspend Mode (EGSM). 1=Host Controller enters the Global Suspend mode.

No USB transactions occur during this time. The Host Controller is able to receive resume

signals from USB and interrupt the system. Software resets this bit to 0 to come out of Global

Suspend mode. Software writes this bit to 0 at the same time that Force Global Resume (bit 4)

is written to 0 or after writing bit 4 to 0. Software must also ensure that the Run/Stop bit (bit 0)

is cleared prior to setting this bit.

Global Reset (GRESET). When this bit is set, the Host Controller sends the global reset signal

on the serial bus and then resets all its logic, including the internal hub registers. The hub

registers are reset to their power on state. This bit is reset by the software after a minimum of

10 ms has elapsed as specified in chapter 7 of the USB Specification.

Note: 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). When this bit is set to a 1, 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. This bit is reset by the Host Controller

when the reset process is complete.

The HCRESET acts on Hub registers are slightly different for 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 (connect status

change) and bit 3 (port enable/disable change) of the PORTSC 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.

Run/Stop (RS). 1=Run. 0=Stop. When set to a 1, the Host Controller proceeds with execution

of the schedule. The Host Controller continues execution as long as this bit is set. When this

bit is set to 0, the Host Controller 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 errors.

PIIX3 Scheda tecnica(PDF) 81 Page - Intel Corporation

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