USB2502-HT View Datasheet(PDF) - SMSC -> Microchip
Part Name
Description
MFG CO.
'USB2502-HT' PDF : 44 Pages View PDF
2-Port USB 2.0 Hub Controller
Datasheet
5.6.1 External Hardware RESET_N
A valid hardware reset is defined as, assertion of RESET_N for a minimum of 1us after all power
supplies are within operating range. While reset is asserted, the Hub (and its associated external
circuitry) consumes less than 500μA of current from the upstream USB power source (300μA for the
Hub and 200μA for the external circuitry).
Assertion of RESET_N (external pin) causes the following:
1. All downstream ports are disabled, and PRTPWR power to downstream devices is removed.
2. The PHYs are disabled, and the differential pairs will be in a high-impedance state.
3. All transactions immediately terminate; no states are saved.
4. All internal registers return to the default state (in most cases, 00(h)).
5. The external crystal oscillator is halted.
6. The PLL is halted.
7. LED indicators are disabled.
The Hub is “operational” 500μs after RESET_N is negated.
Once operational, the Hub immediately reads OEM-specific data from the external EEPROM (if the
SMBus option is not disabled).
5.6.1.1 RESET_N for Strapping Option Configuration
Hardware
reset
asserted
Read Strap
Options
Drive Strap
Attach
Start
Outputs to
inactive
levels
USB
Upstream
USB Reset
recovery
Idle
completion
request
response
t1
t5
t2
t3
RESET_N
t6
t7
t8
VSS
t4
Strap Pins
VSS
Don’t Care
Valid
Don’t Care
Driven by Hub if strap is an output.
Figure 5.2 Reset_N Timing for Default/Strap Option Mode
Table 5.5 Reset_N Timing for Default/Strap Option Mode
NAME
DESCRIPTION
t1
RESET_N Asserted.
t2
Strap Setup Time
t3
Strap Hold Time.
t4
hub outputs driven to inactive logic states
t5
USB Attach (See Note).
MIN
TYP
MAX
1
16.7
16.7
1400
2.0
1.5
100
UNITS
μsec
nsec
nsec
μsec
msec
SMSC USB2502
33
DATASHEET
Revision 2.3 (08-27-07)
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