Datasheet

 2002-2013 Microchip Technology Inc. DS21734B-page 19
TC654/TC655
6.3 CONFIGURATION REGISTER
(CONFIG)
The Configuration Register is an 8-bit read/writable
multi-function control register. This register allows the
user to clear fan faults, select RPM resolution, select
V
OUT
duty cycle (fan speed) control method, select the
fan current pulses per rotation for fans 1 & 2 (for fan
RPM calculation) and put the TC654/TC655 device into
a shutdown mode to save power consumption. See
Register 6-3 below for the Configuration Register bit
descriptions.
REGISTER 6-3: CONFIGURATION REGISTER (CONFIG)
R/W-0 R/W-0 R/W-0 R/W-0 R/W-1 R/W-0 R/W-1 R/W-0
FFCLR RES DUTYC F2PPR F2PPR F1PPR F1PPR SDM
bit 7 bit 0
bit 7 FFCLR: Fan Fault Clear
1 = Clear Fan Fault. This will reset the Fan Fault bits in the Status Register and the FAULT
output.
0 = Normal Operation (default)
bit 6 RES: Resolution Selection for RPM Output Registers
1 = RPM Output Registers (RPM1 & RPM2) will be set for 25 RPM (9-bit) resolution.
0 = RPM Output Registers (RPM1 & RPM2) will be set for 50 RPM (8-bit) resolution. (default)
bit 5 DUTYC: Duty-Cycle Control Method
1 = The V
OUT
duty-cycle will be controlled via the SMBus interface. The value for the V
OUT
duty-cycle will be taken from the duty-cycle register (DUTY_CYCLE).
0 = The V
OUT
duty-cycle will be controlled via the V
IN
analog input pin. The V
OUT
duty-cycle
value will be between 30% and 100% for V
IN
values between 1.62 V and 2.6 V typical. If
the V
IN
pin is open when this mode is selected, the V
OUT
duty-cycle will default to 39.33%.
(default)
bit 4-3 F2PPR: Fan 2 Pulses Per Rotation
The TC654/TC655 device uses this setting to understand how many current pulses per revolu-
tion Fan 2 should have. It then uses this as part of the calculation for the fan 2 RPM value in
the RPM2 Register. See Section 7.7 for application information on determining your fan’s
number of current pulses per revolution.
00 =1
01 = 2 (default)
10 =4
11 =8
bit 2-1 F1PPR: Fan 1 Pulses Per Rotation
The TC654/TC655 device uses this setting to understand how many current pulses per revolu-
tion Fan 1 should have. It then uses this as part of the calculation for the fan 1 RPM value for
the RPM1 Register. See Section 7.7 for application information on determining your fan’s
number of current pulses per revolution.
00 =1
01 = 2 (default)
10 =4
11 =8
bit 0 SDM: Shutdown Mode
1 = Shutdown Mode. See Section 4.9 for more information on low power shutdown mode.
0 = Normal Operation. (default)
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ’1’ = Bit is set ’0’ = Bit is cleared x = Bit is unknown