ADM1033
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The ADM1033 can be configured so that Fan 1 can be
controlled by either the local temperature, or by the Remote 1
temperatures.
Table 31. DRIVE BHVR BITS
Bits DRIVE x BHVR
00 Local Temperature Controls Fan
01 Remote 1 Temperature Controls Fan
10 Reserved
11 Fan Runs at Full Speed
Look-up Table Hysteresis
The user can program a hysteresis to be applied to the
look-up table. The advantage of this is apparent if the
temperature is cycling around one of the threshold
temperatures and causing the fan speed to switch between
the two speeds, particularly when the look-up table is
configured in discrete mode. It would not be as important in
the linear mode.
Table 32. PROGRAMMING THE HYSTERESIS
Code Hysteresis Value
0000 0000 0C
0000 0001 1C
0000 0010 2C
0000 0101 5C
0000 1000 8C
0000 1111 15C
The look-up table’s hysteresis register is at Address 0x3A.
A hysteresis value of between 0C and 15C can be
programmed with a resolution of 1C and applied to all the
temperature thresholds. Table 32 gives examples of values
for programming.
Programming the THERM Limit for Temperature
Channels
THERM is the absolute maximum temperature allowed
on a temperature channel. Above this temperature, a
component such as the CPU or VRM may be operating
beyond its safe operating limit. When the temperature
measured exceeds THERM
, all fans are driven at full speed
to provide critical system cooling. The fans remain running
at full speed until the temperature drops below THERM
–
Hysteresis. The hysteresis value is programmable; its
default is 5C. If the Boost Disable bit (Bit 1) is set in
Configuration Register 2, the fan do not run to full speed.
The THERM
limit is considered the maximum worst-case
operating temperature of the system. Exceeding any
THERM
limit runs the fan at full speed, a condition with
very negative acoustic effects. This limit should be set up as
a fail-safe and not exceeded under normal system operating
conditions. The THERM
temperature limit registers are
listed in Table 33.
Table 33. THERM HYSTERESIS REGISTERS
Address Description Default
0x0D Local THERM Limit 0x95 (85C)
0x10 Remote 1 THERM Limit 0x95 (85C)
The THERM hysteresis register is at Address 0x1A. A
hysteresis value is programmed and applied to all two
temperature channels; Local and Remote 1. A THERM
hysteresis value of between 0C and 15C can be programmed
with a resolution of 1C. Table 33 gives some examples.
Table 34. PROGRAMMING THERM HYSTERESIS
Code Hysteresis Value
0000 0000 0C
0000 0001 1C
0000 0010 2C
0000 0101 5C = Default
0000 1000 8C
0000 1111 15C
XOR Tree Test Mode
The ADM1033 includes an XOR tree test mode. This is
useful for in circuit test equipment at board level testing. By
applying stimulus to the pins included in the XOR test, it is
possible to detect opens or shorts on the system board.
Figure 43 shows the signals that are exercised in the XOR
tree test mode. The XOR tree test is enabled by setting the
XOR bit (Bit 3) in Configuration 4 Register (0x04).
Figure 43. XOR Tree Test
ALERT
LOCATION
FAN_FAULT/REF
THERM
TACH1
DRIVE2
DRIVE1
Lock Bit
Setting the Lock bit (Bit 6) of Configuration Register 1
(Address 0x01) makes all the lockable registers read-only.
These registers remain read-only until the ADM1033 is
powered down and back up again. For more information on
which registers are lockable, see Table 35.
SW Reset
Setting the Software Reset bit (Bit 0) of Configuration
Register 2 (Address 0x02) resets all software resettable bits
to their default value. For more information on resetting
registers and their default values, see Table 35 to Table 69.
