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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors—USB 2.0 Host Controller
Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
Developer’s Manual
August 2006
374
Order Number: 306262-004US
Table 134.
USBCMD – USB Command Register (Sheet 1 of 2)
Field
Description
R,
(Reserved)
These bits are reserved and should be zero.
ITC[7:0]
Interrupt Threshold Control —Read/Write. Default 08h. The system software uses this
field to set the maximum rate at which the host controller will issue interrupts. ITC contains
the maximum interrupt interval measured in micro-frames. Valid values are shown below.
Value Maximum Interrupt Interval
00h
Immediate (no threshold)
01h 1
micro-frame
02h 2
micro-frames
04h 4
micro-frames
08h 8
micro-frames
10h 16
micro-frames
20h 32
micro-frames
40h 64
micro-frames
SUTW
Setup TripWire – Read/Write. This bit is used as a semaphore when the 8 bytes of setup
data read extracted from a QH by the DCD. If the setup lockout mode is off, it there exists a
hazard when new setup data arrives and the DCD copying setup from the QH for a previous
setup packet. This bit is set and cleared by software and will be cleared by hardware when a
hazard exists.
ATDTW
Add dTD TripWire – Read/Write. This bit is used as a semaphore when a dTD is added to
an active (primed) endpoint. This bit is set and cleared by software. This bit must also be
cleared by hardware when its state machine is hazard region where adding a dTD to a primed
endpoint may go unrecognized.
ASPE
Asynchronous Schedule Park Mode Enable (OPTIONAL)
⎯
Read/Write Software uses
this bit to enable or disable Park mode. When this bit is one, Park mode is enabled. When this
bit is a zero, Park mode is disabled.
This field is set to “1” in this implementation.
ASP[1:0]
Asynchronous Schedule Park Mode Count (OPTIONAL)
⎯
Read/Write. It contains a
count of the number of successive transactions the host controller is allowed to execute from a
high-speed queue head on the Asynchronous schedule before continuing traversal of the
Asynchronous schedule. See
“Asynchronous Schedule Park Mode” on page 447
for full
operational details. Valid values are 1h to 3h. Software must not write a zero to this bit when
Park Mode Enable is a one as this will result in undefined behavior.
This field is set to 3h in this implementation.
LR
Light Host Controller Reset (OPTIONAL) — Read Only. Not Implemented. This field will
always be “0”.
IAA
Interrupt on Async Advance Doorbell — Read/Write. This bit is used as a doorbell by
software to tell the host controller to issue an interrupt the next time it advances
asynchronous schedule. Software must write a 1 to this bit to ring the doorbell.
When the host controller has evicted all appropriate cached schedule states, it sets the
Interrupt on Async Advance status bit in the USBSTS register. If the Interrupt on Sync
Advance Enable bit in the USBINTR register is one, then the host controller will assert an
interrupt at the next interrupt threshold.
The host controller sets this bit to zero after it has set the Interrupt on Sync Advance status bit
in the USBSTS register to one. Software should not write a one to this bit when the
asynchronous schedule is inactive. Doing so will yield undefined results.
This bit is only used in host mode.
ASE
Asynchronous Schedule Enable — Read/Write. Default 0b. This bit controls whether the
host controller skips processing the Asynchronous Schedule.
Values meaning
0 Do not process the Asynchronous Schedule.
1 Use the ASYNCLISTADDR register to access the Asynchronous Schedule.
Only the host controller uses this bit.