Intel 1.00 GHz YK80542KC0013M User Manual

87

THRMALERT# signal (see 

 for more details). At power up, the appropriate alarm 

register values need to be programmed into the thermal sensing device via the SMBus. It is 
recommended that the upper thermal reference threshold byte (provided in the processor 
information ROM) be used for setting the upper threshold value in the alarm register.

When polling the thermal sensing device on the processor to read the processor temperatures, it is 
recommended that the polling frequency be every 0.5 to 1 second.

The thermal sensing device 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 is used for sending one-
shot commands only. The receive byte packet accesses the register commanded by the last read 
byte packet. 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. 

 through 

 

diagram the five packet types. In these tables, ‘S’ represents the SMBus start bit, ‘P’ represents a 
stop bit, ‘Ack’ represents an acknowledge, and ‘///’ represents a negative acknowledge. The shaded 
bits are transmitted by the thermal sensor and the unshaded bits are transmitted by the SMBus host 
controller. 

 shows the encoding of the command byte.

1

7  bits

1

1

8  bits

1

8  bits

1

1

1

7  bits

1

1

8  bits

1

1

7 bits

1

1

8 bits

1

1

1

7  bits

1

1

8  bits

1

1

7  bits

1

1

8 bits

1

1

1

0001 100

1

1

1001 1011

1

1