TC654_14 Datasheet, PDF (20/38 Pages) Microchip Technology – Dual SMBus™ PWM Fan Speed Controllers With Fan Fault Detection

TC654/TC655
6.4 STATUS REGISTER (STATUS)
The Status register provides all the information about
what is going on within the TC654/TC655 devices. Fan
fault information, V_IN status, RPM counter overflow,
and over-temperature indication are all available in the
Status register. The Status register is an 8-bit Read-
Only register with bits 6 and 7 unused. See Register 6-
4 below for the bit descriptions.
REGISTER 6-4: STATUS REGISTER (STATUS)
U-0
U-0
R-X
R-0
R-0
R-X
R-0
R-0
—
—
OTF
R2CO
R1CO
VSTAT
F2F
F1F
bit 7
bit 0
bit 7-6
bit 5
bit 4
bit 3
bit 2
bit 1
bit 0
Unimplemented: Read as ‘0’
OTF: Over-Temperature Fault Condition
For the TC654/TC655 device, this bit is set to the proper state immediately at start-up and is therefore
treated as an unknown (X). If V_IN is greater than the threshold required for 100% duty cycle on V_OUT
(2.6V typical), then the bit will be set to a ‘1’. If it is less than the threshold, the bit will be set to ‘0’. This
is determined at power-up.
1 = Over-Temperature condition has occurred.
0 = Normal operation. V_IN is less than 2.6V.
R2CO: RPM2 Counter Overflow
1 = Fault condition. The maximum RPM reading of 12775 RPM in register RPM2 has been exceeded.
This bit will automatically reset to zero when the RPM reading comes back into range.
0 = Normal operation. RPM reading is within limits (default).
R1CO: RPM1 Counter Overflow
1 = Fault condition. The maximum RPM reading of 12775 RPM in register RPM1 has been exceeded.
This bit will automatically reset to zero when the RPM reading comes back into range.
0 = Normal operation. RPM reading is within limits (default).
VSTAT: V_IN Input Status
For the TC654/TC655 devices, the V_IN pin status is checked immediately at power-up. If no external
thermistor or voltage output network is connected (V_IN is open), this bit is set to a ‘1’. If an external net-
work is detected, this bit is set to ‘0’. If the V_IN pin is open and SMBus operation has not been selected
in the Configuration Register, the V_OUT duty cycle will default to 39.33%.
1 = V_IN is open.
0 = Normal operation. voltage present at V_IN.
F2F: Fan 2 Fault
1 = Fault Condition. The value for fan RPM in the RPM2 Register has fallen below the value set in the
FAN_FAULT2 Threshold Register. The speed of Fan 2 is too low and a fault condition is being indi-
cated. The FAULT output will be pulled low at the same time. This fault bit can be cleared using the
Fan Fault Clear bit (FFCLR (bit 7<0>)) in the Configuration Register.
0 = Normal Operation (default).
F1F: Fan 1 Fault
1 = Fault Condition. The value for fan RPM in the RPM1 Register has fallen below the value set in the
FAN_FAULT1 Threshold Register. The speed of Fan 1 is too low and a fault condition is being indi-
cated. The FAULT output will be pulled low at the same time. This fault bit can be cleared using the
Fan Fault Clear bit (FFCLR (bit 7<0>)) in the Configuration Register.
0 = Normal Operation (default).
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
’1’ = Bit is set
U = Unimplemented bit, read as ‘0’
’0’ = Bit is cleared
x = Bit is unknown
DS20001734C-page 20
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