WG82577LM S LGWS Intel, WG82577LM S LGWS Datasheet - Page 14

• Manufacturer Part Number: WG82577LM S LGWS
• Manufacturer: Intel

Specifications of WG82577LM S LGWS

• Lead Free Status / RoHS Status: Supplier Unconfirmed

2.3.1.3
2.3.1.4
2.3.1.5
7
Bus Timeouts
The 82577 can detect (as a master or a slave) an SMB_CLK timeout on the main
SMBus. If the SMBus clock line is held low for 25 ms, the 82577 aborts the transaction.
As a slave, the 82577 detects the timeout and goes into an idle state. In idle, the slave
releases the SMB_CLK and SMB_DATA lines. Any data that was received before the
timeout might have been processed depending on the transaction.
As a master, the 82577 detects a timeout and issues a STOP on the SMBus at the next
convenient opportunity and then brings the SMBus back to idle (releases SMB_CLK and
SMB_DATA). Any master transaction that the 82577 detects a timeout on is aborted.
Bus Hangs
Although uncommon, SMBus bus hangs can happen in a system. The reason for the
hang is typically an unexpected, asynchronous reset or noise coupled onto the SMBus.
Slaves can contribute to SMBus hangs by not implementing the SMBus timeouts as
specified in SMBus 2.0 specification. Masters or host masters can contribute to SMBus
hangs by not detecting the failures and by not attempting to correct the bus hangs.
Because of the potential bus hang scenario, the 82577 has the capability of detecting a
hung bus. If SMB_CLK or SMB_DATA are stuck low for more than 35 ms, the 82577
forces the bus to idle (both SMB_CLK and SMB_DATA set) if it is the cause of the bus
hang.
Packet Error Code (PEC) Support
PEC is defined in the SMBus 2.0 specification. It is an extra byte at the end of the
SMBus transaction, which is a CRC-8 calculated on all of the preceding bytes (not
including ACKs, NACKs, STARTs, or STOPs) in the SMBus transaction. The polynomial
for this CRC-8 is:
The PEC calculation is reset when any of the following occurs:
• A STOP condition is detected on the host SMBus
• An SMBus hang is detected on the host SMBus
• The SMB_CLK is detected high for ~50 µs
x8 + x2 + x + 1
82577 GbE PHY—Interconnects