www.national.com
258
Revision 1.1
G
Core Logic Module
(Continued)
Offset 48h-4Bh
HcRhDescriptorA Register (R/W)
Reset Value = 01000002h
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.
12
NoOverCurrentProtection.
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.
11
OverCurrentProtectionMode.
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.
9
NoPowerSwitching.
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.
8
PowerSwitchingMode.
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.
Offset 4Ch-4Fh
HcRhDescriptorB Register (R/W)
Reset Value = 00000000h
31:16
PortPowerControlMask.
Global-power switching. This field is only valid if NoPowerSwitching is cleared and Power-
SwitchingMode is set (individual port switching). When set, the port only responds to individual port power switching com-
mands (Set/ClearPortPower). When cleared, the port only responds to global power switching commands
(Set/ClearGlobalPower).
0: Device not removable.
1: Global-power mask.
Port Bit relationship - Unimplemented ports are reserved, read/write 0.
0 = Reserved
1 = Port 1
2 = Port 2
...
15 = Port 15
15:0
DeviceRemoveable.
USB ports default to removable devices.
0: Device not removable.
1: Device removable.
Port Bit relationship
0 = Reserved
1 = Port 1
2 = Port 2
...
15 = Port 15
Unimplemented ports are reserved, read/write 0.
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.
Table 5-42. USB_BAR+Memory Offset: USB Controller Registers (Continued)
Bit
Description