Environmental Monitoring and Control Device
Datasheet
BIT
0
NAME
START
R/W
R/W
DEFAULT
0
DESCRIPTION
When software writes a 1 to this bit, the EMC6D100/EMC6D101 enables
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
EMC6D100/EMC6D101 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 (OD) 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.
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.
The EMC6D100/EMC6D101 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’.)
1
2
LOCK
R/W
R
0
0
READY
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' then:
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'.
b) Status bits may be set.
c) The limit and parameter registers are read-only when the start bit is 1. Only the Current PWM
Duty Cycle and Ready/Lock /Start registers are writeable when the associated fan is in manual
mode. The INTEN bit in register 7Ch is also writeable when the start bit is set.
Note: Once programmed, the register values will be saved when start bit is reset to ‘0’.
SMSC EMC6D100/EMC6D101
Page 45
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
