AMD SC1201, SC1200 Bit Description Offset 38h-3Bh HcFrameRemaining Register RO, Reserved. Read 0s

Core Logic Module - USB Controller Registers - PCIUSB 32579B

Table 6-42. USB_BAR+Memory Offset: USB Controller Registers (Continued)

Bit

Description

Offset 38h-3Bh HcFrameRemaining Register (RO) Reset Value = 00000000h

31FrameRemainingToggle (Read Only). Loaded with FrameIntervalToggle when FrameRemaining is loaded.

30:14 Reserved. Read 0s.

13:0	FrameRemaining (Read Only). When the HC is in the UsbOperational state, this 14-bit field decrements each 12 MHz
	clock period. When the count reaches 0, (end of frame) the counter reloads with FrameInterval. In addition, the counter
	loads when the HC transitions into UsbOperational.
Offset 3Ch-3Fh		HcFmNumber Register (RO)	Reset Value = 00000000h
31:16	Reserved. Read 0s.
15:0	FrameNumber (Read Only). This 16-bit incrementing counter field is incremented coincident with the loading of FrameR-
	emaining. The count rolls over from FFFFh to 0h.
Offset 40h-43h		HcPeriodicStart Register (R/W)	Reset Value = 00000000h
31:14	Reserved. Read/Write 0s.
13:0	PeriodicStart. This field contains a value used by the List Processor to determine where in a frame the Periodic List pro-
	cessing must begin.
Offset 44h-47h		HcLSThreshold Register (R/W)	Reset Value = 00000628h
31:12	Reserved. Read/Write 0s.
11:0	LSThreshold. This field contains a value used by the Frame Management block to determine whether or not a low speed
	transaction can be started in the current frame.
Offset 48h-4Bh		HcRhDescriptorA Register (R/W)	Reset Value = 01000003h
31:24	PowerOnToPowerGoodTime. This field value is represented as the number of 2 ms intervals, ensuring that the power
	switching is effective within 2 ms. Only bits [25:24] are implemented as R/W. The remaining bits are read only as 0. It is not
	expected that these bits be written to anything other than 1h, but limited adjustment is provided. This field should be written
	to support system implementation. This field should always be written to a non-zero value.
23:13	Reserved. Read/Write 0s.

12NoOverCurrentProtection. This bit should be written to support the external system port over-current implementation.

0:Over-current status is reported.

1:Over-current status is not reported.

11OverCurrentProtectionMode. This bit should be written 0 and is only valid when NoOverCurrentProtection is cleared.

0:Global Over-Current.

1:Individual Over-Current

10 DeviceType (Read Only). USB is not a compound device.

9NoPowerSwitching. This bit should be written to support the external system port power switching implementation.

0:Ports are power switched.

1:Ports are always powered on.

8PowerSwitchingMode. This bit is only valid when NoPowerSwitching is cleared. This bit should be written 0.

0:Global Switching.

1:Individual Switching

7:0 NumberDownstreamPorts (Read Only). USB supports three downstream ports.

Note: This register is only reset by a power-on reset (PCIRST#). It is written during system initialization to configure the Root Hub. These bit should not be written during normal operation.

AMD Geode™ SC1200/SC1201 Processor Data Book 289