System Management Feature Specifications

Table 6-13. Command Byte Bit Assignment

Register

Command

Reset State

Function

 

 

 

 

RESERVED

00h

N/A

Reserved for future use.

 

 

 

 

RRT

01h

N/A

Read processor core thermal data.

 

 

 

 

RS

02h

N/A

Read status byte (flags, busy signal).

 

 

 

 

RC

03h

0000 0000

Read configuration byte.

 

 

 

 

RCR

04h

0000 0010

Read conversion rate byte.

 

 

 

 

RESERVED

05h

0111 1111

Reserved for future use.

 

 

 

 

RESERVED

06h

1100 1001

Reserved for future use.

 

 

 

 

RRHL

07h

0111 1111

Read processor core thermal diode THIGH limit.

RRLL

08h

1100 1001

Read processor core thermal diode TLOW limit.

WC

09h

N/A

Write configuration byte.

 

 

 

 

WCR

0Ah

N/A

Write conversion rate byte.

 

 

 

 

RESERVED

0Bh

N/A

Reserved for future use.

 

 

 

 

RESERVED

0Ch

N/A

Reserved for future use.

 

 

 

 

WRHL

0Dh

N/A

Write processor core thermal diode THIGH limit.

WRLL

0Eh

N/A

Write processor core thermal diode TLOW limit.

OSHT

0Fh

N/A

One shot command (use send byte packet).

 

 

 

 

RESERVED

10h – FFh

N/A

Reserved for future use.

 

 

 

 

All of the commands are for reading or writing registers in the thermal sensor except the one-shot command (OSHT). The one-shot command forces the immediate start of a new voltage-to- temperature conversion cycle. If a conversion is in progress when the one-shot command is received, then the command is ignored. If the thermal sensing device is in standby mode when the one-shot command is received, a conversion is performed and the sensor returns to standby mode. If the thermal sensor is in auto-convert mode and is between conversions, then the conversion rate timer resets, and the next automatic conversion takes place after a full delay elapses. Please refer to Section 6.7.4 for further detail on standby and auto-convert modes.

The default command after reset is the reserved value (00h). After reset, receive byte packets will return invalid data until another command is sent to the thermal sensing device.

6.7Thermal Sensing Device Registers

The system management software can configure and control the thermal sensor by writing to and interacting with different registers in the thermal sensor. These registers include a thermal reference register, two thermal limit registers, a status register, a configuration register, a conversion rate register, and other reserved registers. The following subsections describe the registers in detail.

6.7.1Thermal Reference Registers

The processor core and thermal sensing device internal thermal reference registers contain the thermal reference value of the thermal sensing device and the processor core thermal diodes. This value ranges from +127 to –128 decimal and is expressed as a two’s complement, eight-bit number. These registers are saturating, that is, values above 127 are represented at 127 decimal, and values below –128 are represented as –128 decimal.

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Datasheet

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Intel Itanium 2 Processor manual Thermal Sensing Device Registers, Thermal Reference Registers, Command Byte Bit Assignment