
Notes
PES32NT24xG2 User Manual
12 - 1
January 30, 2013
®
Chapter 12
SMBus Interfaces
Overview
The PES32NT24xG2 has two SMBus interfaces. The slave SMBus interface provides full access to all
software-visible registers, allowing every register in the device to be read or written by an external SMBus
master. The slave SMBus may also be used to program the serial EEPROM used for initialization. The
Master SMBus interface provides connection for an optional external serial EEPROM used for initialization
and optional external I/O expanders.
Note: While this document makes reference to a Master SMBus interface, the current implementation
of this interface is that of a basic I
2
C master.
Six pins make up each of the two SMBus interfaces. These pins consist of an SMBus clock pin, an
SMBus data pin, and four SMBus address pins. As shown in Figure 12.1, the master and slave SMBuses
may only be used in a split configuration.
The PES32NT24xG2 SMBus master interface does not support SMBus arbitration. As a result, the
switch’s SMBus master must be the only master in the SMBus lines that connect to the serial EEPROM and
I/O expander slaves. In the split configuration, the master and slave SMBuses operate as two independent
buses; thus, multi-master arbitration is not required.
Figure 12.1 Split SMBus Interface Configuration
Master SMBus Interface
The master SMBus interface is used during a switch fundamental reset to load configuration values from
an optional serial EEPROM. It is also used to support I/O expanders used for hot-plug and link status
signals. This interface operates using a basic I
2
C protocol, at a rate of 400 KHz (i.e., I
2
C Fast Mode).
Initialization and I
2
C Reset
Master SMBus initialization occurs during a switch fundamental reset (see section Partition Resets on
page 3-11). If the Switch Mode (SWMODE) signal in the boot vector selects one of the following modes, an
I
2
C reset procedure is performed by the Master SMBus interface during the initialization period.
–
Multi-partition with Unattached ports and I
2
C Reset
–
Multi-partition with Unattached ports and Serial EEPROM initialization with I
2
C Reset.
Processor
Switch
SSMBCLK
SSMBDAT
MSMBCLK
MSMBDAT
SMBus
Master
Other
SMBus
Devices
Serial
EEPROM
...
Hot-Plug
I/O
Expander
Summary of Contents for PCI Express 89HPES32NT24xG2
Page 20: ...IDT Table of Contents PES32NT24xG2 User Manual x January 30 2013 Notes...
Page 24: ...IDT List of Tables PES32NT24xG2 User Manual xiv January 30 2013 Notes...
Page 28: ...IDT List of Figures PES32NT24xG2 User Manual xviii January 30 2013 Notes...
Page 56: ...IDT PES32NT24xG2 Device Overview PES32NT24xG2 User Manual 1 20 January 30 2013 Notes...
Page 100: ...IDT Switch Core PES32NT24xG2 User Manual 4 22 January 30 2013 Notes...
Page 128: ...IDT Failover PES32NT24xG2 User Manual 6 4 January 30 2013 Notes...
Page 148: ...IDT Link Operation PES32NT24xG2 User Manual 7 20 January 30 2013 Notes...
Page 164: ...IDT SerDes PES32NT24xG2 User Manual 8 16 January 30 2013 Notes...
Page 170: ...IDT Power Management PES32NT24xG2 User Manual 9 6 January 30 2013 Notes...
Page 196: ...IDT Transparent Switch Operation PES32NT24xG2 User Manual 10 26 January 30 2013 Notes...
Page 244: ...IDT SMBus Interfaces PES32NT24xG2 User Manual 12 40 January 30 2013 Notes...
Page 247: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 3 January 30 2013 Notes...
Page 248: ...IDT General Purpose I O PES32NT24xG2 User Manual 13 4 January 30 2013 Notes...
Page 330: ...IDT Switch Events PES32NT24xG2 User Manual 16 6 January 30 2013 Notes...
Page 342: ...IDT Multicast PES32NT24xG2 User Manual 17 12 January 30 2013 Notes...
Page 344: ...IDT Temperature Sensor PES32NT24xG2 User Manual 18 2 January 30 2013 Notes...
Page 384: ...IDT Register Organization PES32NT24xG2 User Manual 19 40 January 30 2013...
Page 492: ...IDT Proprietary Port Specific Registers PES32NT24xG2 User Manual 21 44 January 30 2013 Notes...
Page 588: ...IDT NT Endpoint Registers PES32NT24xG2 User Manual 22 96 January 30 2013 Notes...
Page 710: ...IDT JTAG Boundary Scan PES32NT24xG2 User Manual 25 12 January 30 2013 Notes...
Page 743: ...IDT Usage Models PES32NT24xG2 User Manual 26 33 January 30 2013 Notes...
Page 744: ...IDT Usage Models PES32NT24xG2 User Manual 26 34 January 30 2013 Notes...