
FRM_NAT
23
System Level Solutions
January 2013
USB 2.0 (USB20SR) Device IP Core User Guide
Value after Reset
:
00h
FRM_NAT
This register tracks frame number as received from the SOF token, and the
frame time.
Table 4-7
shows the Frame Number and Time register
description.
Value after reset:
00000000h
1
RO
Device speed
This bit is used to configure the endpoints according to device speed.
Device sets this bit when it is connected into high speed mode with the Host PC after the
successful speed negotiation. Device clears this bit when it is connected to the Host PC
into full speed mode due to speed negotiation is failed. While the Host PC does not sup-
port EHCI controller or EHCI is disabled, speed negotiation is failed and device is con-
nected into full speed mode. When the device is enabled for high speed mode using
D_SPEED_SEL register and it is attached into full speed mode with the host then the
message will be displayed that device can be connected into high speed mode.
1: Device is attached into high speed mode
0: Device is attached into full speed mode
0
RO
Suspend
This status bit is used to check whether the device is in suspend state or not.
Device sets this bit when it goes into suspend state and clears the bit when it resumes
from suspend state. When the device is in suspend state there would not be any USB
device related operation from the host.
1: Device is suspended
0: Device is active
Table 4-7. Frame Number and Time (FRM_NAT) Register Details
Bit
Access
Description
31:28
RO
Number of frames with the same frame number (this field may be used to determine
current microframe)
27
RO
Reserved
26:16
RO
Frame number as received from SOF token
15:12
RO
Reserved
11:0
RO
Time since last SOF in 0.5 uS
resolution