Intel Itanium 2 Processor manual Thermal Sensing Device Registers, Thermal Reference Registers

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.

88 Datasheet