Datasheet

TC664/TC665
DS21737B-page 20  2002-2013 Microchip Technology Inc.
6.4 STATUS REGISTER (STATUS)
The Status Register provides all the information about
what is going on within the TC664/TC665 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 1, 4, 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 U-0 R-0 R-X U-X R-0
— —OTF— RCO VSTAT —FF
bit 7 bit 0
bit 7-6 Unimplemented: Read as ‘0’
bit 5 OTF: Over Temperature Fault Condition
For the TC664/TC665 device, this bit is set to the proper state immediately at startup and is
therefore treated as an unknown (X). If V
IN
is greater than the threshold required for 100% duty
cycle on V
OUT
(2.6 V 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 2.6 V.
bit 4 Unimplemented: Read as ‘0’
bit 3 RCO: RPM Counter Overflow
1 = Fault condition. The maximum RPM reading of 12775 RPM in register RPM 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).
bit 2 VSTAT: V
IN
Input Status
For the TC664/TC665 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 network 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
.
bit 1 Unimplemented: Read as ‘unknown’
bit 0 FF: Fan Fault
1 = Fault Condition. The value for fan RPM in the RPM Register has fallen below the value set
in the FAN_FAULT Threshold Register. The speed of the fan is too low and a fault condi-
tion is being indicated. 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 Reg-
ister.
0 = Normal Operation (default).
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit
-n = Value at POR ’1’ = Bit is set ’0’ = Bit is cleared x = Bit is unknown