Universal Serial Bus OHCI Host Controller User's Guide

3.20 HC Root Hub B Register (HCRHDESCRIPTORB)
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The HC root hub B register (HCRHDESCRIPTORB) defines several aspects of the USB host controller
root hub functionality. HCRHDESCRIPTORB is shown in Figure 21 and described in Table 21 .
Note: The device does not provide connections from the USB host controller to pins to provide
external port power switching. Systems that implement port power switching must use other
mechanisms to control port power.
Figure 21. HC Root Hub B Register (HCRHDESCRIPTORB)
31 20 19 18 17 16
PPCM[15-4] PPCM[3] PPCM[2] PPCM[1] PPCM[0]
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
15 4 3 2 1 0
DR[15-4] DR[3] DR[2] DR[1] DR[0]
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
LEGEND: R/W = Read/Write; - n = value after reset
Table 21. HC Root Hub B Register (HCRHDESCRIPTORB) Field Descriptions
Bit Field Value Description
31-20 PPCM[15-4] 0 Port power control mask. PPCM[15] through PPCM[4] are reserved.
19 PPCM[3] Port power control mask. PPCM[3] is the port power control mask for downstream port 3. Defines
whether downstream port 3 has port power controlled by the global power control. System software can
update these bits to simplify host controller driver and/or OTG driver coding.
0 Global power control is implemented for downstream port 3.
1 Per-port power control is implemented for downstream port 3.
18 PPCM[2] Port power control mask. PPCM[2] is the port power control mask for downstream port 2. Defines
whether downstream port 2 has port power controlled by the global power control. System software can
update these bits to simplify host controller driver and/or OTG driver coding.
0 Global power control is implemented for downstream port 2.
1 Per-port power control is implemented for downstream port 2.
17 PPCM[1] Port power control mask. PPCM[1] is the port power control mask for downstream port 1. Defines
whether downstream port 1 has port power controlled by the global power control. System software can
update these bits to simplify host controller driver and/or OTG driver coding.
0 Global power control is implemented for downstream port 1.
1 Per-port power control is implemented for downstream port 1.
16 PPCM[0] 0 Port power control mask. PPCM[0] is reserved.
15-4 DR[15-4] 0 Device removable. DR[15] through DR[4] are reserved.
3 DR[3] Device removable. DR[3] is the device removable bit for downstream port 3. Defines whether
downstream port 3 has a removable or nonremovable device.
0 Downstream port 3 may have a removable device attached.
1 Downstream port 3 has a nonremovable device attached.
2 DR[2] Device removable. DR[2] is the device removable bit for downstream port 2. Defines whether
downstream port 2 has a removable or nonremovable device.
0 Downstream port 2 may have a removable device attached.
1 Downstream port 2 has a nonremovable device attached.
1 DR[1] Device removable. DR[1] is the device removable bit for downstream port 1. Defines whether
downstream port 1 has a removable or nonremovable device.
0 Downstream port 1 may have a removable device attached.
1 Downstream port 1 has a nonremovable device attached.
0 DR[0] 0 Device removable. DR[0] is reserved.
Universal Serial Bus OHCI Host Controller28 SPRUFM8 – September 2008
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