Environmental Monitoring and Control Device
Datasheet
Table 8.2 - Temperature vs. Register Reading
TEMPERATURE READING (DEC) READING (HEX)
-127
81h
-127°c
-50
CEh
-50°c
0
00h
32h
0°c
50
127
50°c
7Fh
80h
127°c
(SENSOR
ERROR)
8.6
Registers 28-2Fh: Fan Tachometer Reading
BIT 7
(MSB)
BIT 0
(LSB)
REGISTER
ADDRESS
READ/
WRITE
REGISTER
NAME
DEFAULT
VALUE
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1
28h
29h
2Ah
2Bh
2Ch
2Dh
2Eh
2Fh
R
R
R
R
R
R
R
R
Tach1 LSB
Tach1 MSB
Tach2 LSB
Tach2 MSB
Tach3 LSB
Tach3 MSB
Tach4 LSB
Tach4 MSB
7
15
7
15
7
15
7
15
6
14
6
14
6
14
6
14
5
13
5
13
5
13
5
13
4
12
4
12
4
12
4
12
3
11
3
11
3
11
3
11
2
10
2
10
2
10
2
10
1
9
1
9
1
9
1
9
0
8
0
8
0
8
0
8
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
The Fan Tachometer Reading registers contain the number of 11.111µs periods (90KHz) between full fan
revolutions. Fans produce two tachometer pulses per full revolution. These registers are updated at least
once every second.
This value is represented for each fan in a 16 bit, unsigned number.
The Fan Tachometer Reading registers always return an accurate fan tachometer measurement, even
when a fan is disabled or non-functional, including when the start bit=0.
When one byte of a 16-bit register is read, the other byte latches the current value until it is read, in order
to ensure a valid reading. The order is LSB first, MSB second.
FFFFh indicates that the fan is not spinning, or the tachometer input is not connected to a valid signal
(This could be triggered by a counter overflow).
These registers are read only – a write to these registers has no effect.
8.7
Registers 30-32h: Current PWM Duty
BIT 7
BIT 0
(LSB)
0
REGISTER
ADDRESS
READ/
WRITE
REGISTER
NAME
Fan1 Current
DEFAULT
VALUE
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1
(MSB)
30h
R/W1
7
6
5
4
3
2
1
N/A
SMSC EMC6D100/EMC6D101
Page 42
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
