Intel Itanium 2 Processor - Manual (Page 88)

88 Datasheet
System Management Feature Specifications
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.
6.7 Thermal 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.
6.7.1 Thermal 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.
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 T
HIGH
limit.
RRLL 08h 1100 1001 Read processor core thermal diode T
LOW
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 T
HIGH
limit.
WRLL 0Eh N/A Write processor core thermal diode T
LOW
limit.
OSHT 0Fh N/A One shot command (use send byte packet).
RESERVED 10h – FFh N/A Reserved for future use.