IDT 89HPES24N3A, User Manual

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IDT Clocking, Reset, and Initialization Clock Operation
PES24N3A User Manual 2 - 7 April 10, 2008
Notes
6. If the selected switch operating mode is one that requires initialization from the serial EEPROM and
the Disable Hot Reset Serial EEPROM Initialization (DHRSTSEI) bit is not set in the Switch Control
(SWCTL) register, then the contents of the serial EEPROM are read and the appropriate PES24N3A
registers are updated.
– If an error is detected during loading of the serial EEPROM, then loading of the serial EEPROM
is aborted and the RSTHALT bit is set in the SWCTL register. Error information is recorded in the
SMBUSSTS register.
– When serial EEPROM initialization completes or when an error is detected, the DONE bit in the
SMBUSSTS register is set.
7. If the Reset Halt (RSTHALT) bit is set in the SWCTL register, all of the logic is held in a reset state
except the master and slave SMBuses. The RSTHALT bit is set only under the following two condi-
tions:
– serial EEPROM initialization is enabled in step 6 and an error is detected during loading of the
serial EEPROM or
– the user intentionally sets this bit through the EEPROM code.
8. Normal device operation begins.
The operation of the slave SMBus interface is unaffected by a hot reset. Using the slave SMBus to
access a register that is reset by a hot reset causes zero to be returned on a read and written data to be
ignored on writes. A hot reset initiated by the writing of a one to the Hot Reset (HRST) bit in the Switch
Control (SWCTL) register always results in the PES24N3A returning a completion to the requester before
the hot reset process begins.
Upstream Secondary Bus Reset
An upstream secondary bus reset may be initiated by the following condition:
– A one is written to the Secondary Bus Reset (SRESET) bit in the upstream port’s (i.e., port 0)
Bridge Control Register (BRCTL).
When an upstream secondary bus reset occurs, the following sequence is executed.
1. Each downstream port whose link is up propagates the reset by transmitting TS1 ordered sets with
the hot reset bit set.
2. All registers fields in all registers associated with downstream ports, except those denoted as “sticky”
or Read and Write when Unlocked (i.e, RWL), are reset to their initial value. The value of fields
denoted as “sticky” or RWL is unaffected by an upstream secondary bus reset.
3. All TLPs received from downstream ports and queued in the PES24N3A are discarded.
4. Logic in the stack, application layer and switch core associated with the downstream ports are grace-
fully reset.
5. Wait for the Secondary Bus Reset (SRESET) bit in the Bridge Control Register (BCTL) to clear.
6. Normal downstream port operation begins.
The operation of the upstream port is unaffected by a secondary bus reset. The link remains up and
Type 0 configuration read and write transactions that target the upstream port complete normally. During an
upstream secondary bus reset, all TLPs destined to the secondary side of the upstream port’s PCI-to-PCI
bridge are treated as unsupported requests.
The operation of the slave SMBus interface is unaffected by an upstream secondary bus reset. Using
the slave SMBus to access a register that is reset by an upstream secondary bus reset causes zero to be
returned on a read and written data to be ignored on writes.
Downstream Secondary Bus Reset
A downstream secondary bus reset may be initiated by the following condition:
– A one is written to the Secondary Bus Reset (SRESET) bit in a downstream port’s (i.e., port 0)
Bridge Control Register (BCTRL).