
SMSC LPC47B27x
- 149 -
Rev. 08-10-04
DATASHEET
NAME
REG OFFSET
(hex)
58
(R/W)
DESCRIPTION
Fan Control
Default = 0x50
on VTR POR
Fan Control Register
Bit[0] Fan 1 Clock Source Select
This bit and the Fan 1 Clock Multiplier bit is used with The
Fan 1 Clock Select bit in the Fan 1 register (0x56) to
determine the fan speed F
OUT
. See “Different Modes for
Fan” table (Table 50) in “Fan Speed Control and
Monitoring” section.
Bit[1] Fan 2 Clock Source Select
This bit and the Fan 2 Clock Multiplier bit is used with The
Fan 2 Clock Select bit in the Fan 2 register (0x57) to
determine the fan speed F
OUT
. See “Different Modes for
Fan” table (Table 50) in “Fan Speed Control and
Monitoring” section.
Bit[2] Fan 1 Clock multiplier
0=No multiplier used
1=Double the fan speed selected by bit 0 of this
register and bit 7 of the FAN1
register
Bit[3] Fan 2 Clock multiplier
0=No multiplier used
1=Double the fan speed selected by bit 1 of this
register and bit 7 of the FAN2 register
Bit[5:4] The FAN1 count divisor. Clock scalar for adjusting
the tachometer count. Default = 2.
00: divisor = 1
01: divisor = 2
10: divisor = 4
11: divisor = 8
Bit[7:6] The FAN2 count divisor. Clock scalar for adjusting
the tachometer count. Default = 2.
00: divisor = 1
01: divisor = 2
10: divisor = 4
11: divisor = 8
Fan Tachometer Register 1
Bit]7:0] The 8-bit FAN1 tachometer count. The number of
counts of the internal clock per pulse of the fan. The count
value is computed from Equation 1. This value is the final
(maximum) count of the previous pulse (latched). The
value in this register may not be valid for up to 2 pulses
following a write to the preload register.
Fan Tachometer Register 2
Bit[7:0] The 8-bit FAN2 tachometer count. The number of
counts of the internal clock per pulse of the fan. The count
value is computed from Equation 1. This value is the final
(maximum) count of the previous pulse (latched). The
value in this register may not be valid for up to 2 pulses
following a write to the preload register.
Fan Preload Register 1
Bit[7:0] The FAN1 tachometer preload. This is the initial
value used in the computation of the FAN1 count. Writing
this register resets the tachometer count.
Fan1 Tachometer
Register
Default = 0x00
on VTR POR
59
(R)
Fan2 Tachometer
Register
Default = 0x00
on VTR POR
5A
(R)
Fan1 Preload
Register
Default = 0x00
on VTR POR
Fan2 Preload
Register
Default = 0x00
on VTR POR
5B
(R/W)
5C
(R/W)
Fan Preload Register 2
Bit[7:0] The FAN2 tachometer preload. This is the initial
value used in the computation of the FAN2 count. Writing
this register resets the tachometer count.