Datasheet

Dual-Core Intel® Xeon® Processor 7100 Series Datasheet 111
Features
7.4.7 Thermal Sensor Supported SMBus Transactions
The thermal sensor responds to five of the SMBus packet types: Write Byte, Read Byte,
Send Byte, Receive Byte, and Alert Response Address (ARA). The Send Byte packet can
be used for sending one-shot commands. The Receive Byte packet accesses the
register commanded by the last Read Byte packet and can be used to continuously read
from a register. If a Receive Byte packet was preceded by a Write Byte or send Byte
packet more recently than a Read Byte packet, then the behavior is undefined.
Ta b l e 7 - 8 through Tabl e 7- 12 diagram the five packet types. In these figures, ‘S’
represents the SMBus start bit, ‘P’ represents a stop bit, ‘Ack’ represents an
acknowledge, and ‘///’ represents a negative acknowledge (NACK). The shaded bits are
transmitted by the thermal sensor, and the bits that aren’t shaded are transmitted by
the SMBus host controller.
Note:
1. This is an 8-bit field. The device which sent the alert will respond to the ARA Packet with its address in the
seven most significant bits. The least significant bit is undefined and may return as a ‘1’ or ‘0’. See
Section 7.4.1 for details on the Thermal Sensor Device addressing.
2. The shaded bits are transmitted by the thermal sensor, and the bits that aren’t shaded are transmitted by
the SMBus host controller.
Table 7-8. Write Byte SMBus Packet
S Slave Address Write Ack Command Code Ack Data Ack P
17-bits 0
18-bits18-bits11
Table 7-9. Read Byte SMBus Packet
S
Slave
Address
Write
Ack
Command
Code
Ack S
Slave
Address
Read
Ack Data
/
/
/
P
17-bits 0
18-bits117-bits1 1 8-
bits
11
Table 7-10. Send Byte SMBus Packet
SSlave AddressWrite Ack Command Code Ack P
17-bits 0
18-bits11
Table 7-11. Receive Byte SMBus Packet
SSlave Address Read Ack Data /// P
17-bits 1
1 8-bits 1 1
Table 7-12. ARA SMBus Packet
S ARA Read Ack Address /// P
1 0001 100 1
1 Device Address
1
11