Data Sheet

Ethernet Controller I210 —System Manageability
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10.5.4.2 SMBus ARP Functionality
The I210 supports the SMBus ARP protocol as defined in the SMBus 2.0 specification. The I210 is a
persistent slave address device so its SMBus address is valid after power-up and loaded from the Flash.
The I210 supports all SMBus ARP commands defined in the SMBus specification both general and
directed.
SMBus ARP capability can be disabled through the Flash.
10.5.4.3 SMBus ARP Flow
SMBus ARP flow is based on the status of two flags:
• AV (Address Valid): This flag is set when the I210 has a valid SMBus address.
• AR (Address Resolved): This flag is set when the I210 SMBus address is resolved (SMBus address
was assigned by the SMBus ARP process).
These flags are internal I210 flags and are not exposed to external SMBus devices.
Since the I210 is a Persistent SMBus Address (PSA) device, the AV flag is always set, while the AR flag
is cleared after power up until the SMBus ARP process completes. Since AV is always set, the I210
always has a valid SMBus address.
When the SMBus master needs to start an SMBus ARP process, it resets (in terms of ARP functionality)
all devices on SMBus by issuing either Prepare to ARP or Reset Device commands. When the I210
accepts one of these commands, it clears its AR flag (if set from previous SMBus ARP process), but not
its AV flag (the current SMBus address remains valid until the end of the SMBus ARP process).
Clearing the AR flag means that the I210 responds to SMBus ARP transactions that are issued by the
master. The SMBus master issues a Get UDID command (general or directed) to identify the devices on
the SMBus. The I210 always responds to the Directed command and to the General command only if its
AR flag is not set.
After the Get UDID, The master assigns the I210 SMBus address by issuing an Assign Address
command. The I210 checks whether the UDID matches its own UDID and if it matches, it switches its
SMBus address to the address assigned by the command (byte 17). After accepting the Assign Address
command, the AR flag is set and from this point (as long as the AR flag is set), the I210 does not
respond to the Get UDID General command. Note that all other commands are processed even if the AR
flag is set. The I210 stores the SMBus address that was assigned in the SMBus ARP process in the
Flash, so at the next power up, it returns to its assigned SMBus address.