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DS20001734C-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

fan current pulses per rotation for fans 1 and 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 and RPM2) will be set for 25 RPM (9-bit) resolution.

0

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

bit 5

DUTYC: Duty Cycle Control Method

1

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

0

bit 4-3

F2PPR: Fan 2 Pulses Per Rotation

The TC654/TC655 device uses this setting to understand how many current pulses per revolution 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 “Determining Current Pulses Per Revolution of Fans” 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 revolution 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 “Determining Current Pulses Per Revolution of Fans” 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 “Low-Power Shutdown Mode” 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