Environmental Monitoring and Control Device
Datasheet
7.3
Device Set-Up
BIOS will follow the steps listed below to configure the fan registers on the device. The registers
corresponding to each function are listed. All steps may not be necessary if default values are acceptable.
Regardless of all changes made by the BIOS to the limit and parameter registers during configuration, the
EMC6D100/EMC6D101 will continue to operate based on default values until the Start bit, in the
Ready/Lock/Start register, is set. Once the Start bit is set, the EMC6D100/EMC6D101 will operate
according to the values that were set by BIOS in the limit and parameter registers.
1. Set limits and parameters (not necessarily in this order)
a) [5F-61h] Set PWM frequencies and auto fan control range.
b) [62-63h] Set spike smoothing and min/off
c) [5C-5Eh] Set the fan spin-up delays.
d) [5C-5Eh] Match each fan with a corresponding thermal zone.
e) [67-69h] Set the fan temperature limits.
f) [6A-6Ch] Set the temperature absolute limits.
g) [64-66h] Set the PWM minimum duty cycle.
h) [5F-61h] Set the Auto Fan Control Range.
i) [6D-6Eh] Set the temperature Hysteresis values.
2. [40h] Set bit 0 (Start) to start monitoring.
3. [40h] Set bit 1 (Lock) to lock the limit and parameter registers (optional)
7.4
PWM Fan Speed Control
Note: The following description applies to PWM1, PWM2, and PWM3.
When describing the operation of the PWMs, the terms “Full on” and “100% duty cycle” means that the
PWM output will be high (OD) for 255 clocks, and low for 1 clock (INVERT bit = 0). The exception to this is
during fan spin-up when the PWM pin will be forced high (OD) for the duration of the spin-up time.
Note: During the low time of each PWM output, the part will generate multiple positive pulses for system
synchronization. See section 7.7 System Synchronization on page 36 for a description of these pulses.
7.4.1 MANUAL FAN CONTROL OPERATING MODE
When operating in Manual Fan Control Operating Mode software controls the fans. The operation of the
fans can be monitored based on reading the temperature and tachometer reading registers and/or by
polling the interrupt status registers. The EMC6D100 offers the option of generating an interrupt indicated
by the INT# pin.
To control the fans:
To set the mode to operate in manual mode, write ‘111’ to bits[7:5] Zone/Mode, located in Registers 5Ch-
5Eh: Fan Configuration.
The speed of the fan is controlled by the duty cycle set for that device. The duty cycle must be
programmed in Registers 30h-32h: Current PWM Duty
To monitor the fans:
If an out-of-limit condition occurs, the corresponding status bit will be set in the Interrupt Status registers.
Setting this status bit will generate an interrupt signal on the INT# pin (if enabled – EMC6D100 only).
Software must handle the interrupt condition and modify the operation of the EMC6D100/EMC6D101
accordingly. Software can evaluate the operation of the device through the Temperature and Fan
Tachometer Reading registers.
SMSC EMC6D100/EMC6D101
Page 30
Rev. 09-09-04
DATASHEET
SMSC [ SMSC CORPORATION ]
