Fan Control Device with High Frequency PWM and Temperature Monitors
Datasheet
8.1
Undefined Registers
The registers shown in Table 8.1, "Register Summary" above are the defined registers in the part. Any
reads to undefined registers always return 00h. Writes to undefined registers have no effect and do
not return an error.
8.2
Defined Registers
8.2.1
Registers 20-24h: Voltage Reading
Table 8.2 Registers 20-24h: Voltage Reading
Register
Address
Read/
Write
Bit 7
(MSb)
Bit 0
(LSb)
Default
Value
Register Name
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
21h
22h
R
R
Vccp Reading
VCC Reading
7
7
6
6
5
5
4
4
3
3
2
2
1
1
0
0
N/A
N/A
The Voltage Reading registers reflect the current voltage of the EMC2300 voltage monitoring inputs.
Voltages are presented in the registers at ¾ full scale for the nominal voltage, meaning that at nominal
voltage, each register will read C0h.
Table 8.3 Voltage vs. Register Reading
REGISTER
READING AT
NOMINAL
REGISTER
READING AT
MAXIMUM
REGISTER
READING AT
VOLTAGE MINIMUM VOLTAGE
NOMINAL
INPUT VOLTAGE
MAXIMUM
VOLTAGE
MINIMUM
VOLTAGE
VOLTAGE
Vccp
VCC
2.25V
3.3V
C0h
C0h
3.00V
4.38V
FFh
FFh
0V
0V
00h
00h
The Voltage Reading registers will be updated automatically by the EMC2300 Chip with a minimum
frequency of 4Hz. These registers are read only – a write to these registers has no effect.
8.2.2
Registers 25-27h: Temperature Reading
Table 8.4 Registers 25-27h: Temperature Reading
Register
Address
Read/
Write
Bit 7
(MSb)
Bit 0
(LSb)
Default
Value
Register Name
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
25h
26h
27h
R
R
R
Remote Diode 1 Temp Reading
Internal Temp Reading
7
7
7
6
6
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
0
0
0
N/A
N/A
N/A
Remote Diode 2 Temp Reading
The Temperature Reading registers reflect the current temperatures of the internal and remote diodes.
Remote Diode 1 Temp Reading register reports the temperature measured by the Remote1- and
Remote1+ pins, Remote Diode 2 Temp Reading register reports the temperature measured by the
Remote2- and Remote2+ pins, and the Internal Temp Reading register reports the temperature
measured by the internal (ambient) temperature sensor. Current temperatures are represented as 8
bit, 2’s complement, signed numbers in Celsius, as shown below in Table 8.5. The Temperature
Reading register will return a value of 80h if the remote diode pins are not implemented by the board
designer or are not functioning properly (this corresponds to the diode fault interrupt status bits). The
SMSC EMC2300
Revision 0.2 (06-14-06)
DATA4S9HEET
SMSC [ SMSC CORPORATION ]
