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November 28, 2011

IDT 89HPES32H8G2 Data Sheet

Each of the two SMBus interfaces contain an SMBus clock pin and an SMBus data pin. In addition, the slave SMBus has SSMBADDR1 and

SSMBADDR2 pins. As shown in Figure 3, the master and slave SMBuses may only be used in a split configuration.

Figure 3 Split SMBus Interface Configuration

The switch’s 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.

Hot-Plug Interface

The PES32H8G2 supports PCI Express Hot-Plug on each downstream port. To reduce the number of pins required on the device, the

PES32H8G2 utilizes an external I/O expander, such as that used on PC motherboards, connected to the SMBus master interface. Following reset and

configuration, whenever the state of a Hot-Plug output needs to be modified, the PES32H8G2 generates an SMBus transaction to the I/O expander

with the new value of all of the outputs. Whenever a Hot-Plug input changes, the I/O expander generates an interrupt which is received on the IOEX-

PINTN input pin (alternate function of GPIO) of the PES32H8G2. In response to an I/O expander interrupt, the PES32H8G2 generates an SMBus

transaction to read the state of all of the Hot-Plug inputs from the I/O expander.

General Purpose Input/Output

The PES32H8G2 provides 9 General Purpose Input/Output (GPIO) pins that may be used by the system designer as bit I/O ports. Each GPIO pin

may be configured independently as an input or output through software control. Some GPIO pins are shared with other on-chip functions. These

alternate functions may be enabled via software, SMBus slave interface, or serial configuration EEPROM.

Processor

Switch

SSMBCLK

SSMBDAT

MSMBCLK

MSMBDAT

SMBus

Master

Other

SMBus

Devices

Serial

EEPROM

...

Hot-Plug

I/O

Expander