IDT 89HPES12N3, User Manual

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IDT Clocking, Reset, and Initialization Reset
PES12N3 User Manual 2 - 7 June 7, 2006
Notes
Hot reset is only propagated downstream. TS1 ordered-sets indicating a hot reset received on a down-
stream port do not result in a hot reset of the downstream port or any function inside the switch.
When a globally initiated hot reset occurs, all of the logic associated with the transparent bridges, stacks
and the switch core are reset except for the PLLs, SerDes, master SMBus interface, slave SMBus interface,
and some registers. Regardless of the switch operating mode, a hot-reset does not result in reloading of the
serial EEPROM.
The value of register fields denoted as “sticky” or as Read and Write when Unlocked (i.e., RWL) are
preserved in all ports across a hot-reset. All other register fields in all ports are reset to their initial values.
When a hot reset is initiated globally, each downstream port shall send a hot-reset message to its link
partner prior to being reset.
Globally Initiated Hot Reset To Downstream Ports
A hot reset is initiated globally to downstream ports when the following condition occurs
– A one is written to the Secondary Bus Reset (SRESET) bit in the upstream port’s (port A) Bridge
Control Register (BCTRL). See BCTRL - Bridge Control (0x03E) on page 9-25.
When a globally initiated hot reset is initiated to downstream ports, all of the logic associated with the
transparent bridges, stacks and FIFOs in the switch core associated with the downstream ports are reset
except for the PLLs, SerDes, master SMBus interface, slave SMBus interface, and some registers. Regard-
less of the switch operating mode, it does not result in reloading of the serial EEPROM.
The value of register fields denoted as “sticky” or as Read and Write when Unlocked (i.e., RWL) in
downstream ports are preserved. All other register fields are reset to their initial values.
When a hot reset is initiated globally to downstream ports, each downstream port shall send a hot-reset
message to its link partner prior to being reset.
Unlike a globally initiated hot reset to the entire device, a globally initiated hot reset to downstream ports
does not affect the state of the upstream port’s configuration register except those required to update port
status.
Locally Initiated Hot Reset to a Downstream Port
A hot reset is initiated locally to a downstream port by writing to the SRESET bit of a downstream port’s
BCTRL registers. When this occurs, a hot-reset message is sent on that port to its link partner. After the
message is sent, the phy layer is effectively reset.
A locally initiated hot reset does not affect the state of any port (i.e., transparent bridge) configuration
register except those required to update port status.