Data Sheet

Ethernet Controller I210 —System Manageability
654
— Power state change
There can be cases where the MC is hung and not responding to the SMBus notification. The I210 has a
time-out value (defined in the Flash) to avoid hanging while waiting for the notification response. If the
MC does not respond until the time out expires, the notification is de-asserted and all pending data is
silently discarded.
Note that the SMBus notification time-out value can only be set in the Flash. The MC cannot modify this
value.
10.5.5.1 SMBus Alert and Alert Response Method
The SMBus Alert# (SMBALERT_N) signal is an additional SMBus signal that acts as an asynchronous
interrupt signal to an external SMBus master. The I210 asserts this signal each time it has a message
that it needs the MC to read and if the chosen notification method is the SMBus alert method. Note that
the SMBus alert method is an open-drain signal which means that other devices besides the I210 can
be connected on the same alert pin. As a result, the MC needs a mechanism to distinguish between the
alert sources.
The MC can respond to the alert by issuing an ARA Cycle command to detect the alert source device.
The I210 responds to the ARA cycle with its own SMBus slave address (if it was the SMBus alert source)
and de-asserts the alert when the ARA cycle is completes. Following the ARA cycle, the MC issues a
read command to retrieve the I210 message.
Some BMCs do not implement the ARA cycle transaction. These BMCs respond to an alert by issuing a
Read command to the I210 (0xC0/0xD0 or 0xDE). The I210 always responds to a Read command, even
if it is not the source of the notification. The default response is a status transaction. If the I210 is the
source of the SMBus Alert, it replies the read transaction and then de-asserts the alert after the
command byte of the read transaction.
Note: In SMBus Alert mode, the SMBALERT_N pin is used for notification. In multiple-address mode,
all devices generate alerts on events that are independent of each other.
The ARA cycle is an SMBus receive byte transaction to SMBus Address 0001-100b. Note that the ARA
transaction does not support PEC. The ARA transaction format is as follows:
10.5.5.2 Asynchronous Notify Method
When configured using the asynchronous notify method, the I210 acts as a SMBus master and notifies
the MC by issuing a modified form of the write word transaction. The asynchronous notify transaction
SMBus address and data payload is configured using the Receive Enable command or using the Flash
defaults. Note that the asynchronous notify is not protected by a PEC byte.
1711 8 111
S Alert Response Address Rd A Slave Device Address A P
0001 100 1 0
Manageability Slave SMBus
Address
01
1711711
S Target Address Wr A Sending Device Address A ...
MC Slave Address 0 0 MNG Slave SMBus Address 0 0