TC654 datasheet(19/36 Pages) MICROCHIP

19 / 36 page

 2002 Microchip Technology Inc.

DS21734A-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

VOUT 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

descriptions.

CONFIGURATION REGISTER (CONFIG)

R/W-0

R/W-1

R/W-0

R/W-1

R/W-0

FFCLR

RES

DUTYC

F2PPR

F1PPR

SDM

bit 7

bit 0

bit 7

FFCLR: Fan Fault Clear

= Clear Fan Fault. This will reset the Fan Fault bits in the Status Register and the FAULT

output.

= Normal Operation (default)

bit 6

RES: Resolution Selection for RPM Output Registers

= RPM Output Registers (RPM1 & RPM2) will be set for 25 RPM (9-bit) resolution.

= RPM Output Registers (RPM1 & RPM2) will be set for 50 RPM (8-bit) resolution. (default)

bit 5

DUTYC: Duty-Cycle Control Method

= The VOUT duty-cycle will be controlled via the SMBus interface. The value for the VOUT

duty-cycle will be taken from the duty-cycle register (DUTY_CYCLE).

= The VOUT duty-cycle will be controlled via the VIN analog input pin. The VOUT duty-cycle

value will be between 30% and 100% for VIN values between 1.62 V and 2.6 V typical. If

the VIN pin is open when this mode is selected, the VOUT 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.

= 2 (default)

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.

= 2 (default)

bit 0

SDM: Shutdown Mode

= Shutdown Mode. See Section 4.9 for more information on low power shutdown mode.

= 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

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