
P
P
- 17 - 
 Andigilog, Inc. 2006 
www.andigilog.com
October 2006 - 70A06010 
aSC7621
Temperature Measurement 
Diode temperatures are measured with a precision Delta-V
BE
 methodology converted to a digital temperature reading by a 
10-bit sigma-delta converter. PECI interface to the CPU provide Digital Thermometer readings of substrate temperature. The 
measurement system provides a means for assigning any of the temperature inputs to a Temperature Zone. The user may 
set limits on these readings to be continuously monitored and alarm bits set when they are exceeded. Separately, the 
measurements are also delivered to the automatic fan control system to adjust fan speed. The following registers contain the 
readings from the internal and remote sensors. 
Registers 25-10h, 26-15h and 27-0Eh: Temperature Zone Readings (10-Bit, 2’s Complement Reporting) 
Register 
Address 
Read/ 
Write 
Register Name 
Bit 7 
(MSB)
Bit 6 
Bit 5 
Bit 4 
Bit 3 
Bit 2 
Bit 1 
Bit 0 
(LSB) 
Default 
Value 
25h 
R 
Zone 1 Temper-
ature (MS Byte) 
9 
8 
7 
6 
5 
4 
3 
2 
N/A 
10h 
R 
Zone 1 Temper-
ature (LS Byte) 
1 
0 
X 
X 
X 
X 
X 
X 
N/A 
26h 
R 
Zone 2 Temper-
ature (MS Byte) 
9 
8 
7 
6 
5 
4 
3 
2 
N/A 
15h 
R 
Zone 2 Temper-
ature (LS Byte) 
1 
0 
X 
X 
X 
X 
X 
X 
N/A 
27h 
R 
Zone 3 Temper-
ature (MS Byte) 
9 
8 
7 
6 
5 
4 
3 
2 
N/A 
16h 
R 
Zone 3 Temper-
ature (LS Byte) 
1 
0 
X 
X 
X 
X 
X 
X 
N/A 
33h 
R 
Zone 4 Temper-
ature (MS Byte) 
Zone 4 Temper-
ature (LS Byte) 
9 
8 
7 
6 
5 
4 
3 
2 
N/A 
17h 
R 
1 
0 
X 
X 
X 
X 
X 
X 
N/A 
The Temperature Zone registers reflect the current temperature of the internal and remote diodes or PECI CPU Digital 
Thermometers. Filtering is applied to all readings and this is described in the Spike & Smoothing Filter section below. Any 
temperature input may be assigned to any zone, according to the settings in the Zone Assignment Registers, [02h] and 
[03h]. The default assignment is as follows: 
Zone 1 Temperature register reports the temperature measured by the thermal diode connected to the Remote 1- and 
Remote 1+ pins if either: 
1. PECI monitoring is disabled (register [40h] bit 4=0) 
2. PECI monitoring is enabled but in legacy mode, (register [36h] bit 4, LEG = 0).  
If PECI Monitoring is enabled (register [40h] bit 4=1) AND legacy mode is LEG = legacy mode (register [36h] bit 4, LEG = 1), 
the register reports the highest Digital Thermometer reading by the processor. 
Zone 2 Temperature register reports the temperature measured by the internal (junction) temperature sensor. 
Zone 3 Temperature register reports the temperature measured by the thermal diode connected to the second set of Remote 
2- and Remote 2+ pins.  
Zone 4 reports temperatures as follows: 
1. By default and if PECI temperature is disabled (register [36h] bit 4, LEG = 0) the Zone 4 register is not used. In this 
case, special temperature value of 80h will be reported to indicate that no temperature is available. If this zone is 
associated with any fan PWM controller(s), this will result in these controller(s) being overridden to 100% duty cycle. 
No error bits will be set in the Interrupt Status Registers. 
2. If PECI Monitoring is enabled [40h] bit 4=1) AND legacy mode is in standard mode (register [36h] bit 4, LEG = 0), 
the register will report the highest Digital Thermometer reading by the processor. 
3. Temperatures are represented as 10-bit, 2’s complement, signed numbers, in degrees Celsius, as shown below in 
Table 3. 
4. If PECI Monitoring is enabled [40h] bit 4=1) AND legacy mode is in legacy mode (register [36h] bit 4, LEG = 1), the 
register will report the temperature measured by the thermal diode connected to the Remote 1- and Remote 1+ 
pins.