LM96000CIMT National Semiconductor, LM96000CIMT Datasheet - Page 18

• Manufacturer Part Number: LM96000CIMT
• Description: IC,Data Acquisition System,7-CHANNEL,8-BIT,TSSOP,24PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LM96000CIMT

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

www.national.com
Register
Address
5Ch
5Dh
5Eh
Functional Description
to ensure that the limit is high enough not to cause sporadic alerts. The fan tachometer will not cause a bit to be set in Interrupt
Status Register 2 if the current value in Current PWM Duty registers is 00h or if the fan 1 disabled via the Fan Configuration
Register. Interrupts will never be generated for a fan if its minimum is set to FF FFh.
Given the insignificance of Bit 0 and Bit 1, these bits could be programmed to remember which fan is which, as follows.
Setting the Ready/Lock/Start/Override register Lock bit has no effect these registers.
4.14 Registers 5C-5Eh: Fan Configuration
This register becomes Read Only when the Ready/Lock/Start/Override register Lock bit is set. Any further attempts to write to this
register shall have no effect. After power up the default value is used whenever the Ready/Lock/Start/Override register Start bit
is cleared even though modifications to this register are possible.
Bits [7:5] Zone/Mode
Bits [7:5] of the Fan Configuration registers associate each fan with a temperature sensor. When in Auto Fan Mode the fan will
be assigned to a zone, and its PWM duty cycle will be adjusted according to the temperature of that zone. If ‘Hottest’ option is
selected (101 or 110), the fan will be controlled by the hottest of zones 2 and 3, or of zones 1, 2, and 3. To determine the ‘Hottest’
zone the PWM level for each zone is calculated then the the highest PWM value is selected. When in manual control mode, the
Current PWM duty registers (30h-32h) become Read/Write. It is then possible to control the PWM outputs with software by writing
to these registers. When the fan is disabled (100) the corresponding PWM output should be driven low (or high, if inverted).
Bit [4] PWM Invert
Bit [4] inverts the PWM output. If set to 0, 100% duty cycle will yield an output that is always high. If set to 1, 100% duty cycle
will yield an output that is always low.
Bit [3] Reserved
Bits [2:0] Spin Up
Bits [2:0] specify the ‘spin up’ time for the fan. When a fan is being started from a stationary state, the PWM output is held at 100%
duty cycle for the time specified in the table below before scaling to a lower speed.
Zone 1: External Diode 1 (processor)
Zone 2: Internal Sensor
Zone 3: External Diode 2
Read/
Write
R/W
R/W
R/W
Register
Name
Fan1 Configuration
Fan2 Configuration
Fan3 Configuration
ZON[2:0]
000
001
010
011
100
101
110
111
Fan
CPU
Memory
Chassis Front
Chassis Rear
(Continued)
Bit 7
(MSB)
ZON2
ZON2
ZON2
Fan Configuration
Fan on zone 1 auto
Fan on zone 2 auto
Fan on zone 3 auto
Fan always on full
Fan disabled
Fan controlled by hottest of zones 2, 3
Fan controlled by hottest of zones 1, 2, 3
Fan manually controlled (Test Mode)
TABLE 4. Fan Zone Setting
Bit 6
ZON1
ZON1
ZON1
Bit 5
ZON0
ZON0
ZON0
18
Bit 4
INV
INV
INV
Bit 1
0
0
1
1
Bit 3
RES
RES
RES
Bit 2
SPIN2
SPIN2
SPIN2
Bit 0
0
1
0
1
Bit 1
SPIN1
SPIN1
SPIN1
Bit 0
(LSB)
SPIN0
SPIN0
SPIN0
Default
Value
62h
62h
62h
Lock?
U
U
U