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© Andigilog, Inc. 2006
www.andigilog.com
October 2006 - 70A06010
aSC7621
Temperature
Temperature Limit
(2’s Complement)
>127°C
0111
1111
+127°C (Default High)
0111
1111
+125°C
0111
1101
+90°C
0101
1010
+50°C
0011
0010
+25°C
0001
1001
0°C
0000
0000
-50°C
1100
1110
-127°C (Default Low)
1000
0001
Table 20 Temperature Zone High- and Low-Limit Registers - 8-Bit Two’s Complement
Register 5C-5Eh: Fan Temperature Zone Assignment and Spin-up Mode
Register
Address
Read/
Write
Register Name
Bit 7
(MSB)
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
(LSB)
Default
Value
Lock
5Ch
R/W
Fan 1 Configuration
ZON2
ZON1
ZON0
INV
ALT
SPIN2
SPIN1
SPIN0
62
X
5Dh
R/W
Fan 2 Configuration
ZON2
ZON1
ZON0
INV
ALT
SPIN2
SPIN1
SPIN0
62
X
5Eh
R/W
Fan 3 Configuration
ZON2
ZON1
ZON0
INV
ALT
SPIN2
SPIN1
SPIN0
62
X
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.
Bits [7:5] Zone/Mode and Bit [3] Alternate Zone/Mode
Bits [7:5] of the Fan Configuration registers associate each fan with a Temperature Zone. 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 (110), the fan will be controlled by the the hottest of zones 1, 2 or 3. To determine the “hottest zone”, the
PWM level for each zone is calculated then the zone with the higher PWM value (not temperature) is selected. When in
manual control mode, the Current PWM duty register (30-32h) 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-3 enables an alternate set of definitions for the ZON[2:0] Zone/Mode bits described in Table 21.
Fan Configuration ALT = 0
ZON [2:0]
Fan Configuration ALT = 1
ZON[2:0]
Fan on zone 1.
000
Fan on zone 4.
000
Fan on zone 2.
001
Fan controlled by hottest of zones 1, 2, 3, and 4.
001
Fan on zone 3.
010
Reserved. (Fan on full. PWM = 255.)
010
Fan on full. PWM = 255.
011
Reserved. (Fan on full. PWM = 255.)
011
Fan disabled. PWM = 0.
100
Vendor specific. (Fan on full. PWM = 255.)
100
Fan controlled by hottest of 2, or 3.
101
Vendor specific. (Fan on full. PWM = 255.)
101
Fan controlled by hottest of zones 1, 2, and 3.
110
Vendor specific. (Fan on full. PWM = 255.)
110
Fan Manually controlled (Test Mode)
111
Vendor specific. (Fan on full. PWM = 255.)
111
Table 21 Fan Zone Setting
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 [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.
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