USB2512A Standard Microsystems Corp., USB2512A Datasheet - Page 28

• Manufacturer Part Number: USB2512A
• Description: Usb2512a Usb 2.0 High-speed 2-port Hub Controller
• Manufacturer: Standard Microsystems Corp.

Revision 1.96 (07-11-08)
4.6.2
4.6.2.1
RESET_N
Strap Pins
NAME
t1
t2
t3
t4
t5
t6
VSS
VSS
Hardware
asserted
reset
RESET_N Asserted.
Strap Setup Time
Strap Hold Time.
hub outputs driven to inactive logic states
USB Attach (See Note).
Host acknowledges attach and signals USB
Reset.
Don’t Care
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.
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.
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).
RESET_N for Strapping Option Configuration
Read Strap
t1
Options
Figure 4.3 Reset_N Timing for Default/Strap Option Mode
Table 4.3 Reset_N Timing for Default/Strap Option Mode
t2
Valid
DESCRIPTION
t3
t4
Don’t Care
Drive Strap
Outputs to
inactive
levels
DATASHEET
t5
28
Upstream
Attach
USB
Driven by Hub if strap is an output.
16.7
16.7
MIN
100
1
USB Reset
recovery
t6
USB 2.0 Hi-Speed 2-Port Hub Controller
TYP
1.5
t7
Idle
MAX
1400
100
2
SMSC USB2512A
t8
completion
response
request
Start
UNITS
Datasheet
msec
msec
μsec
nsec
nsec
μsec