USB 2.0 Hi-Speed Hub Controller
Datasheet
8.6.1.3
RESET_N for SMBus Slave Configuration
Hardware
reset
asserted
Reset
Negation
Attach
SMBus Code
Hub PHY
USB
Load
Stabilization
Upstream
USB Reset
recovery
Idle
Start
completion
request
response
t1
RESET_N
t2
t3
t4
t5
t6
t7
VSS
Figure 8.5 Reset_N Timing for SMBus Mode
Table 8.9 Reset_N Timing for SMBus Mode
NAME
t1
t2
t3
t4
t5
t6
t7
DESCRIPTION
RESET_N Asserted.
Hub Recovery/Stabilization.
SMBus Code Load (See Note).
Hub Configuration and USB Attach.
Host acknowledges attach and signals USB
Reset.
USB Idle.
Completion time for requests (with or without data
stage).
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
prior to (or coincident with) the assertion of RESET_N.
100
Undefined
5
250
MIN
1
500
300
100
TYP
MAX
UNITS
μsec
μsec
msec
msec
msec
msec
msec
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 ]
