2-Port USB 2.0 Hi-Speed Hub Controller
Datasheet
DS00001726A-page 20
2014 Microchip Technology Inc.
Chapter 4 Configuration Options
Microchip’s USB 2.0 hub is fully compliant with the
USB Specification
. Refer to Chapter 10 (Hub
Specification) for general details regarding hub operation and functionality.
The hub provides one Transaction Translator (TT) that is shared by both downstream ports (defined
as Single-TT configuration). The TT contains 4 non-periodic buffers.
4.1
Hub Configuration
The USB2422 only supports internal defaults with the exception of the non-removable strap option
(using
NON_REM[1:0]
). The hub internal default settings are as follows:
Internal Default Configuration without over-rides
Strap options enabled
Self-powered operation enabled
Individual power switching
Individual over-current sensing
4.2
Resets
There are two device resets: a hardware reset via
RESET_N
, and a USB Bus Reset.
4.2.1
External Hardware RESET_N
A valid hardware reset is defined as assertion of
RESET_N
for a minimum of 1
μ
s after all power
supplies are within operating range. While reset is asserted, the hub (and its associated external
circuitry) consumes less than 500
μ
A of current from the upstream USB power source.
Assertion of
RESET_N
causes the following:
1. All downstream ports are disabled.
2. The
PRTPWR
power to downstream devices is turned on when battery charging is enabled for a
specific port, and removed when battery charging is disabled for a specific port.
3. The PHYs are disabled, and the differential pairs will be in a high-impedance state.
4. All transactions immediately terminate; no states are saved.
5. All internal registers return to the default state (in most cases, 00h).
6. The external crystal oscillator is halted.
Table 4.1 Hub Configuration Options
CFG_SEL
DESCRIPTION
0
Default configuration:
Strap options enabled
Hub descriptors indicate the hub as “self-powered”
1
The hub is configured externally over SMBus (as an SMBus
slave device with address 0101100b):
Strap options disabled
Self-powered or bus-powered depending on register
settings
All registers configured over SMBus
