Intel Itanium 2 Processor manual Thermal Limit Registers, Status Register, Configuration Register

System Management Feature Specifications

6.7.2Thermal Limit Registers

The thermal sensing device has two thermal limit registers; they define high and low limits for the processor core thermal diode. The encoding for these registers is the same as for the thermal reference registers. If the diode thermal value equals or exceeds one of its limits, then its alarm bit in the status register is triggered. This indication is also brought out to the Itanium 2 processor system bus via the THRMALERT# signal.

6.7.3Status Register

The status register shown in Table 6-14indicates which (if any) of the thermal value thresholds have been exceeded. It also indicates if a conversion is in progress or if an open circuit has been detected in the processor core thermal diode connection. Once set, alarm bits stay set until they are cleared by a status register read. A successful read to the status register will clear any alarm bits that may have been set, unless the alarm condition persists. Note that the THRMALERT# interrupt signal is latched and is not automatically cleared when the status flag bit is cleared. The latch is cleared by sending the Alert Response Address (0001100) on the SMBus.

Table 6-14. Thermal Sensing Device Status Register

	Bit	Name	Function
7	(MSB)	BUSY	A one indicates that the device’s analog to digital converter is busy converting.
6		RESERVED	Reserved for future use.
5		RESERVED	Reserved for future use.
4		RHIGH	A one indicates that the processor core thermal diode high temperature alarm has
			been activated.
3		RLOW	A one indicates that the processor core thermal diode low temperature alarm has
			been activated.
2		OPEN	A one indicates an open fault in the connection to the processor core diode.
1		RESERVED	Reserved for future use.
0	(LSB)	RESERVED	Reserved for future use.

6.7.4Configuration Register

The configuration register controls the operating mode (standby vs. auto-convert) of the thermal sensing device. Table 6-15shows the format of the configuration register. If the RUN/STOP bit is set (high) then the thermal sensing device immediately stops converting and enters standby mode. The thermal sensing device will still perform analog-to-digital conversions in standby mode when it receives a one-shot command. If the RUN/STOP bit is clear (low) then the thermal sensor enters auto-conversion mode. The thermal sensing device starts operating in free running mode, auto- converting at 0.25 Hz after power-up.

Table 6-15. Thermal Sensing Device Configuration Register

Bit	Name	Reset	Function
		State
7 (MSB)	RESERVED	0	Reserved for future use.
6	RUN/STOP	0	Standby mode control bit. If high, the device immediately stops
			converting, and enters standby mode. If low, the device converts in either
			one-shot or timer mode.
5–0	RESERVED	0	Reserved for future use.

Datasheet 89