2013 - 2015 Microchip Technology Inc. DS00001726B-page 23
USB2422
4.4.7 CONFIGURATION DATA BYTE 1 REGISTER (CFG1)
Address: 06h Size: 8 bits
Bits Description Type Default
7 Self or Bus Power (SELF_BUS_PWR)
Selects between Self- and Bus-Powered operation.
The Hub is either Self-Powered (draws less than 2mA of upstream bus
power) or Bus-Powered (limited to a 100mA maximum of upstream power
prior to being configured by the host controller).
When configured as a Bus-Powered device, the Hub consumes less than
100mA of current prior to being configured. After configuration, the Bus-
Powered Hub (along with all associated hub circuitry, any embedded devices
if part of a compound device, and 100mA per externally available
downstream port) must consume no more than 500mA of upstream VBUS
current. The current consumption is system dependent, and the OEM must
ensure that the USB2.0 specifications are not violated.
When configured as a Self-Powered device, <1mA of upstream VBUS
current is consumed and all ports are available, with each port being capable
of sourcing 500mA of current.
This field is set by the OEM using the SMBus interface option.
Please see the description under Dynamic Power for the self/bus power
functionality when dynamic power switching is enabled.
0 = Bus-Powered operation
1 = Self-Powered operation
Note: If Dynamic Power Switching is enabled, this bit is ignored and the
LOCAL_PWR pin is used to determine if the hub is operating from
self or bus power.
R/W 0b
6 RESERVED --
5 High Speed Disable (HS_DISABLE)
Disables the capability to attach as either a High/Full- speed device, and
forces attachment as Full-speed only i.e. (no High-Speed support).
0 = High-/Full-Speed
1 = Full-Speed-Only (High-Speed disabled)
R/W 0b
4 Multi-TT Enable (MTT_ENABLE)
Enables one transaction translator per port operation.
Selects between a mode where only one transaction translator is available
for all ports (Single-TT), or each port gets a dedicated transaction translator
(Multi-TT)
Note: The host may force Single-TT mode only
0 = Single TT for all ports. Default to STT if MTT still exists
1 = One TT per port (multiple TT’s supported)
R/W 0b
