USB2503-HZH Standard Microsystems Corp., USB2503-HZH Datasheet - Page 31

• Manufacturer Part Number: USB2503-HZH
• Description: Interface, Integrated USB2.0 Compatible 3-Port Hub
• Manufacturer: Standard Microsystems Corp.

Integrated USB2.0 Compatible 3-Port Hub
Datasheet
SMSC USB2503
5.5
5.6
5.6.1
The SMSC Hub can be configured via a combination of internal default values and pin strap options.
Please see
default/pin-strap configuration option.
The strapping option pins only cover a limited sub-set of the configuration options. The internal default
values will be used for the bits & registers that are not controlled by a strapping option pin. Please
refer to
The Green LED pins are sampled after RESET_N negation, and the logic values are used to configure
the hub if the internal default configuration mode is selected. The implementation shown below (see
Figure
configuration, the LED functions with active low signalling, and the PAD will “sink” the current from the
external supply. When a pin is configured with a “Strap Low” configuration, the LED functions with
active high signalling, and the PAD will “source” the current to the external LED.
There are two different resets that the Hub experiences. One is a hardware reset (via the RESET_N
pin) and the second is a USB Bus Reset.
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.
Default Strapping Options:
Reset
5.1) shows a recommended passive scheme. When a pin is configured with a “Strap High”
Table 5.1 on page 13
Table 4.1, "3-Port Hub Pin Descriptions"
Figure 5.1 LED Strapping Option
HUB
for the internal default values that are loaded when this option is selected.
GR2
GR1
26
50K
50K
+V
for specific details on how to enable the
Strap High
Strap Low
Revision 1.3 (08-24-04)