USB 2.0 Hi-Speed Hub Controller
Datasheet
8.6.1.3
RESET_N for SMBus Slave Configuration
Start
completion
request
response
Hardware
reset
asserted
Attach
USB
Upstream
Reset
Negation
SMBus Code
Load
Hub PHY
Stabilization
USB Reset
recovery
Idle
t6
t7
t1
t5
t2
t3
t4
RESET_N
VSS
Figure 8.5 Reset_N Timing for SMBus Mode
Table 8.9 Reset_N Timing for SMBus Mode
NAME
DESCRIPTION
MIN
TYP
MAX
UNITS
t1
t2
t3
t4
t5
RESET_N Asserted.
1
μsec
μsec
msec
msec
msec
Hub Recovery/Stabilization.
SMBus Code Load (See Note).
Hub Configuration and USB Attach.
500
300
100
250
Host acknowledges attach and signals USB
Reset.
100
t6
t7
USB Idle.
Undefined
msec
msec
Completion time for requests (with or without data
stage).
5
Notes:
For bus-powered configurations, the 99.5 ms (MAX) is required, and the hub and its associated
circuitry must not consume more than 100 mA from the upstream USB power source during
t2+t3+t4+t5+t6+t7. For Self-Powered configurations, t3 MAX is not applicable and the time to load
the configuration is determined by the external SMBus host.
All power supplies must have reached the operating levels mandated in Chapter 9, DC Parameters,
prior to (or coincident with) the assertion of RESET_N.
8.6.2
USB Bus Reset
In response to the upstream port signaling a reset to the hub, the hub does the following:
Note: The hub does not propagate the upstream USB reset to downstream devices.
1. Sets default address to 0.
2. Sets configuration to: Unconfigured.
3. Negates PRTPWR[x:1] to all downstream ports unless battery charging (BC_EN) is enabled.
4. Clears all TT buffers.
5. Moves device from suspended to active (if suspended).
Revision 1.0 (3-11-09)
58
SMSC USB251x
DATASHEET
SMSC [ SMSC CORPORATION ]
