
Dual-Core Intel Itanium Processor 9000 Series Datasheet
81
System Management Feature Specifications
6.1.3
SMBus Device Addressing
Of the addresses broadcast across the SMBus, the memory components claim those of
the form “1010XXYZb”. The “XX” and “Y” bits are used to enable the devices on the
processor at adjacent addresses. The Y bit is hard-wired on the processor to GND (‘0’)
for the Scratch EEPROM and pulled to 3.3V (‘1’) for the processor information ROM. The
“XX” bits are defined by the processor socket via the SMA0 and SMA1 pins on the
processor connector. These address pins have a weak pull-down (10 kΩ) to ensure that
the memory components are in a known state in systems which do not support the
SMBus, or only support a partial implementation. The “Z” bit is the read/write bit for
the serial bus transaction.
The thermal sensing device internally decodes 1 of 3 upper address patterns from the
bus of the form “0011XXXZb”, “1001XXXZb” or “0101XXXZb”. The device’s addressing,
as implemented, uses SMA2 and SMA1 and includes a Hi-Z state for the SMA2 address
pin. Therefore, the thermal sensing device supports six unique resulting addresses. To
set the Hi-Z state for SMA2, the pin must be left floating. The system should drive
SMA1 and SMA0, and will be pulled low (if not driven) by the 10 kΩ pull-down resistor
on the processor substrate. Attempting to drive either of these signals to a Hi-Z state
would cause ambiguity in the memory device address decode, possibly resulting in the
devices not responding, thus timing out or hanging the SMBus. As before, the “Z” bit is
the read/write bit for the serial bus transaction.
describe the address pin connections and how they affect the addressing of the
devices.
Note:
Addresses of the form “0000XXXXb” are Reserved and should not be generated by an
SMBus master. Also, system management software must be aware of the processor
select in the address for the thermal sensing device.
Table 6-2.
Thermal Sensing Device SMBus Addressing on the Dual-Core Intel Itanium
2 Processor 9000 Series
Address (Hex)
Upper Address1
Notes:
1. Upper address bits are decoded in conjunction with the select pins.
Processor Select
8-Bit Address Word on Serial Bus
SMA2
SMA1
b[7:0]
3Xh
0011
0
0011000Xb
0011
0
1
0011010Xb
5Xh
0101
Z2
2. A tri-state or “Z” state on this pin is achieved by leaving this pin unconnected.
0
0101001Xb
0101
Zb
1
0101011Xb
9Xh
1001
1
0
1001100Xb
1001
1
1001110Xb