MEC1404 Datasheet, PDF (374/572 Pages) Microchip Technology – Keyboard and Embedded Controller Products for Notebook PC

MEC140X/1X
26.11.2 TACHX STATUS REGISTER
Offset ^04h
Bits
Description
Type
31:4 Reserved
3 COUNT_READY_STATUS
This status bit is asserted when the TACHx input changes state and
when the counter value is latched. This bit remains cleared to '0'
when the TACH_READING_MODE_SELECT bit in the TACHx Con-
trol Register is '0'.
When the TACH_READING_MODE_SELECT bit in the TACHx Con-
trol Register is set to '1', this bit is set to ‘1’ when the counter value is
latched by the hardware. It is cleared when written with a ‘1’. If
COUNT_READY_INT_EN in the TACHx Control Register is set to 1,
this status bit will assert the Tach Interrupt signal.
R
R/WC
Default
-
0b
Reset
Event
-
nSYSRS
T
1=Reading ready
0=Reading not ready
2 TOGGLE_STATUS
This bit is set when TACHx Input changes state. It is cleared when
written with a ’1’. If TACH_INPUT_INT_EN in the TACHx Control
Register is set to ’1’, this status bit will assert the Tach Interrupt sig-
nal.
R/WC
0b
nSYSRS
T
1=TACHx Input changed state (this bit is set on a low-to-high or high-
to-low transition)
0=TACHx stable
1 TACH_PIN_STATUS
R
This bit reflects the state of TACHx Input. This bit is a read only bit
that may be polled by the embedded controller.
0b
nSYSRS
T
1= TACHx Input is high
0= TACHx Input is low
0 TACH_OUT_OF_LIMIT_STATUS
This bit is set when the Tach Count value is greater than the high
limit or less than the low limit. It is cleared when written with a ’1’. To
disable this status event set the limits to their extreme values. If
TACH_OUT_OF_LIMIT_ENABLE in the TACHx Control Register is
set to 1’, this status bit will assert the Tach Interrupt signal.
R/WC
0b
nSYSRS
T
Note:
Note:
1=Tach is outside of limits
0=Tach is within limits
Some fans offer a Locked Rotor output pin that generates a level event if a locked rotor is detected. This bit
may be used in combination with the Tach pin status bit to detect a locked rotor signal event from a fan.
Tach Input may come up as active for Locked Rotor events. This would not cause an interrupt event because
the pin would not toggle. Firmware must read the status events as part of the initialization process, if polling
is not implemented.
DS00001956D-page 374
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