Fan Control Device with Hardware Monitoring and Acoustic Noise Reduction Features
Datasheet
7.2.9
Register 40h: Ready/Lock/Start Monitoring
Register
Address
Read/
Bit 7
Bit 0
Default
Value
Register Name
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Write
(MSb)
(LSb)
40h
R/W
Ready/Lock/Start
RES
RES
RES
RES
OVRID
READY
LOCK
START
00h
Setting the Lock bit makes the Lock and Start bits read-only.
BIT
NAME
R/W DEFAULT
DESCRIPTION
When software writes a 1 to this bit, the EMC6D102 enables
0
START
R/W
0
monitoring and PWM output control functions based on the limit and
parameter registers. Before this bit is set, the part does not update
register values. Whenever this bit is set to 0, the monitoring and PWM
output control functions are based on the default limits and parameters,
regardless of the current values in the limit and parameter registers.
The EMC6D102 preserves the values currently stored in the limit and
parameter registers when this bit is set or cleared. This bit becomes
read only when the Lock bit is set.
Note:
When this bit is 0, all fans are on full 100% duty cycle, i.e.,
PWM pins are high for 255 clocks, low for 1 clock. When this
bit is 0, the part is not monitoring.
It is expected that all limit and parameter registers will be set by BIOS
or application software prior to setting this bit because these registers
cannot be written once the start bit is set.
1
2
LOCK
R/W
R
0
0
Setting this bit to 1 locks specified limit and parameter registers. Once
this bit is set, limit and parameter registers become read only and will
remain locked until the device is powered off. This register bit becomes
read only once it is set.
READY
The EMC6D102 sets this bit automatically after the part is fully
powered up, has completed the power-up-reset process, and after all
A/D converters are functioning (all bias conditions for the A/Ds have
stabilized and the A/Ds are in operational mode). (Always reads back
‘1’.)
3
OVRID
R/W
R
0
0
If this bit is set to 1, all PWM outputs go to 100% duty cycle regardless
of whether or not the lock bit is set.
4-7
Reserved
Reserved.
Note: There is a start-up time of up to 82ms for monitoring after the start bit is set to ‘1’, during which
time the reading registers are not valid.
The following summarizes the operation of the part based on the Start bit:
1. If Start bit = '0' then:
a. Fans are set to Full On.
b. No voltage, temperature, or fan tach monitoring is performed. The values in the reading registers
will be N/A (Not Applicable), which means these values will not be considered valid readings until
the Start bit = '1'. The exception to this is the Tachometer reading registers, which always give the
actual reading on the TACH pins.
c. No Status bits are set.
2. If Start bit = '1'
a. All fan control and monitoring will be based on the current values in the registers. There is no need
to preserve the default values after software has programmed these registers because no
monitoring or auto fan control will be done when Start bit = '0'.
SMSC EMC6D102
Revision 0.4 (04-05-05)
DATA5S3HEET
SMSC [ SMSC CORPORATION ]
