IDT SMBus Interfaces
PES12T3G2 User Manual
5 - 2
January 28, 2013
Notes
Master SMBus Interface
The master SMBus interface is used during a Fundamental Reset to load configuration values from an
optional serial EEPROM. It is also used to support optional I/O expanders used for hot-plug and other
status signals.
Initialization
Master SMBus initialization occurs during a Fundamental Reset (see section Fundamental Reset on
page 2-3). During a Fundamental Reset initialization sequence, the state of the Master SMBus Slow Mode
(MSMBSMODE) signal is examined. If this signal is asserted, then the Master SMBus Clock Prescalar
(MSMBCP) field in the SMBus Control (SMBUSCTL) register is initialized to support 100 KHz SMBus oper-
ation. If the signal is negated, then the MSMBCP field is initialized for 400 KHz SMBus operation.
Serial EEPROM
During a Fundamental or Hot Reset, an optional serial EEPROM may be used to initialize any software
visible register in the device. Serial EEPROM loading occurs if the Switch Mode (SWMODE[2:0]) field
selects an operating mode that performs serial EEPROM initialization. The address used by the SMBus
interface to access the serial EEPROM is specified by the MSMBADDR[4:1] signals as shown in Table 5.1.
Device Initialization from a Serial EEPROM
During initialization from the optional serial EEPROM, the master SMBus interface reads configuration
blocks from the serial EEPROM and updates corresponding registers in the PES12T3G2. Any PES12T3G2
software visible register in any port may be initialized with values stored in the serial EEPROM. Each soft-
ware visible register in the PES12T3G2 has a CSR system address which is formed by adding the PCI
configuration space offset value of the register to the base address of the configuration space in which the
register is located. Configuration blocks stored in the serial EEPROM use this CSR system address shifted
right two bits (i.e., configuration blocks in the serial EEPROM use doubleword CSR system addresses and
not byte CSR system addresses). Base addresses for the PCI configuration spaces in the PES12T3G2 are
listed in Table 8.1, Base Addresses for Port Configuration Space Registers on page 8-1. Since configura-
tion blocks are used to store only the value of those registers that are initialized, a serial EEPROM much
smaller than the total size of all of the configuration spaces may be used to initialize the device. Any serial
EEPROM compatible with those listed in Table 5.2 may be used to store the PES12T3G2 initialization
values. Some of these devices are larger than the total size of all of the PCI configuration spaces in the
PES12T3G2 that may be initialized and thus may not be fully utilized.
Address Bit
Address Bit Value
1
MSMBADDR[1]
2
MSMBADDR[2]
3
MSMBADDR[3]
4
MSMBADDR[4]
5
1
6
0
7
1
Table 5.1 Serial EEPROM SMBus Address
Содержание 89HPES12T3G2
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Страница 12: ...IDT List of Tables PES12T3G2 User Manual vi January 28 2013 Notes...
Страница 14: ...IDT List of Figures PES12T3G2 User Manual viii January 28 2013 Notes...
Страница 18: ...IDT Register List PES12T3G2 User Manual xii January 28 2013 Notes...
Страница 46: ...IDT Link Operation PES12T3G2 User Manual 3 10 January 28 2013 Notes...
Страница 66: ...IDT SMBus Interfaces PES12T3G2 User Manual 5 18 January 28 2013 Notes...
Страница 70: ...IDT Power Management PES12T3G2 User Manual 6 4 January 28 2013 Notes...
Страница 138: ...IDT Configuration Registers PES12T3G2 User Manual 8 62 January 28 2013 Notes...