Datasheet

USB251xB/xBi
DS00001692C-page 38  2010 - 2015 Microchip Technology Inc.
5.5.1.3 RESET_N for SMBus Slave Configuration
Note 5-3 All power supplies must have reached the operating levels mandated in Section 6.0, "DC
Parameters", prior to (or coincident with) the assertion of RESET_N.
Note 5-4 10 ms for hubs, 50 ms for root ports.
5.5.2 USB BUS RESET
In response to the upstream port signaling a reset to the hub, the hub does the following:
1. Sets default internal USB address to 0
2. Sets configuration to: unconfigured
3. Negates PRTPWR[x:1] to all downstream ports unless battery charging (BC_EN[x:1]) is enabled
4. Clears all TT buffers
5. Moves device from suspended to active (if suspended)
6. Complies with Section 11.10 of the
USB 2.0 Specification [1] for behavior after completion of the reset sequence.
The host then configures the hub and the hub’s downstream port devices in accordance with the
USB Specifica-
tion
.
FIGURE 5-3: RESET_N TIMING FOR SMBUS MODE
Name Description MIN TYP MAX Units
t1 RESET_N Asserted 1 s
t2 CFG_SEL[1:0] setup time 16.7 ns
t3 CFG_SEL[1:0] hold time 16.7 1400 ns
t4 Hub recovery/stabilization 500
s
t5 SMBus Code Load 2 1000 ms
t6 Hub configuration and USB attach 0 ms
t7 Host acknowledges attach and signals USB reset 100 ms
t8 USB_RESET host-defined ms
t9 USB_RESET State Note 5-4 ms
t10 USB Reset Recovery 10 ms
Note: The hub does not propagate the upstream USB reset to downstream devices.
t1
t4
t6 t7 t8 t9
RESET_N
VSS
Hardware
reset asserted
Read
CFG_SEL[1:0]
SMBus code
load
Attach USB
upstream
Attach
Debounce
Interval
USB_RESET
USB_RESET
State
t5
Hub PHY
stabilization
valid
CFG_SEL[2:0]
VSS
don’t care don’t care
t2
t3
t10
USB Reset
Recovery