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© Andigilog, Inc. 2006
www.andigilog.com
August 2006 - 70A05003
aSC7512
Temperature Measurement
Temperatures are measured with a precision Delta-VBE methodology converted to a digital temperature reading by a 10-bit
sigma-delta converter. 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 and 26-15h: Zone Temperature Reading (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
Temperature
9
8
7
6
5
4
3
2
00
10h
R
Zone 1
Temperature (LS
Byte)
1
0
X
X
X
X
X
X
00
26h
R
Zone 2
Temperature
9
8
7
6
5
4
3
2
00
15h
R
Zone 2
Temperature (LS
Byte)
1
0
X
X
X
X
X
X
00
The Zone Temperature registers reflect the current temperature of the internal and remote diodes. Processor (Zone 1)
Temp register reports the temperature measured by the thermal diode connected to the Remote - and Remote + pins.
Internal (Zone 2) Temp register reports the temperature measured by the internal (junction) temperature sensor.
Temperatures are represented as 10 bit, 2’s complement, signed numbers, in Celsius, as shown below in Table 1.
The Temperature Reading register will return a value of 8000h if the remote diode pins are not used by the board designer or
are not functioning properly. This reading will cause the zone limit bit (bit 4) in the Interrupt Status Register (41h) and the
remote diode fault status bit (bit 6) in the Interrupt Status Register 2 (42h) to be set. These registers are read-only – a write
to these registers has no effect.
Digital Output (2’s Complement)
High Byte
Low Byte
Temperature
10-Bit Resolution
Ignore
+125°C
0111
1101
00
XX
XXXX
+100°C
0110
0100
00
XX
XXXX
+50°C
0011
0010
00
XX
XXXX
+25°C
0001
1001
00
XX
XXXX
+10°C
0000
1010
00
XX
XXXX
+1.75°C
0000
0001
11
XX
XXXX
+0.25°C
0000
0000
01
XX
XXXX
0°C
0000
0000
00
XX
XXXX
-1.75°C
1111
1110
01
XX
XXXX
-55°C
1100
1001
00
XX
XXXX
Table 1 Relationship between Temperature and 2’s Complement Digital Output, -55°C to +125°C
Temperature Measurement Configuration and ALERT Limits
Registers 09h, 0Ah, 0Fh, 22h: Conversion Rate and ALERT Configuration
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
09h
R/W
Configuration
Alert
Mask
Run/
Stop
Alert/
Tach
RES
RES
RES
RES
RES
00
0Ah
R/W
Conversion Rate
CONV7
CONV6
CONV5
CONV4
CONV3
CONV2
CONV1
CONV0
08
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