WG82574L S LBA8 Intel, WG82574L S LBA8 Datasheet - Page 203

• Manufacturer Part Number: WG82574L S LBA8
• Manufacturer: Intel

Specifications of WG82574L S LBA8

• Operating Supply Voltage (typ): 3.3V
• Operating Temp Range: 0C to 85C
• Operating Temperature Classification: Commercial
• Mounting: Surface Mount
• Pin Count: 64
• Lead Free Status / RoHS Status: Compliant

System Manageability—82574 GbE Controller
8.4.5.1
Figure 45.
8.4.5.2
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 82574 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 82574 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 82574 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
82574 message.
Some MCs do not implement the ARA cycle transaction. These MCs respond to an alert
by issuing a Read command to the 82574 (0xC0/0xD0 or 0xDE). The 82574 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 82574 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.
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:
SMBus ARA Cycle Format
Asynchronous Notify Method
When configured using the asynchronous notify method, the 82574 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 NVM defaults. Note that the
asynchronous notify is not protected by a PEC byte.
S
1
1
S
Alert Response Address
MC Slave Address
Target Address
0001 100
7
7
Wr
1
0
Rd
1
1
1
A
0
1
A
0
MNG Slave SMBus Address
Sending Device Address
Manageability Slave SMBus
Slave Device Address
Address
7
8
1
0
1
0
1
A
0
1
A
1
. . .
1
P
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