LM93 datasheet(16/92 Pages) NSC

16 / 92 page

12.0 Functional Description

(Continued)

mented to a max count for an above temperature trip and

decremented to zero when below the trip temperature set-

ting, to remove the trip.

The minimum time for PROCHOT assertion is time depen-

dant on the FSB frequency. The minimum time that the

processor asserts PROCHOT is estimated to be 187 µs.

12.10 PROCHOT MONITORING

PROCHOT monitoring applies to both the P1_PROCHOT

and P2_PROCHOT inputs. Both inputs are monitored in the

same fashion, but the following description discusses a

single

monitor.

(Px_PROCHOT

represents

both

P1_PROCHOT and P2_PROCHOT).

PROCHOT monitoring is meant to achieve two goals. One

goal is to measure the percentage of time that PROCHOT is

asserted over a programmable time period. The result of this

measurement can be read from an 8-bit register where one

LSB equals 1/256th of the PROCHOT Time Interval (0.39%).

The second goal is to have a status register that indicates,

as a coarse percentage, the amount of time a processor has

been throttled. This second goal is required in order to

communicate information over the NIC using ASF, i.e. status

can be sent, not values.

To achieve the first goal, the PROCHOT input is monitored

over a period of time as defined by the PROCHOT Time

Interval Register. At the end of each time period, the 8-bit

measurement is transferred to the Current Px_PROCHOT

Current Px_PROCHOT register value is moved to the Aver-

age Px_PROCHOT register by adding the new value to the

old value and dividing the result by 2. Note that the value that

is averaged into the Average Px_PROCHOT register is not

the new measurement but rather the previous measurement.

If the SMBus writes to the Current P1_PROCHOT (or Cur-

rent P2_PROCHOT) register, the capture cycle restarts for

both

monitoring

channels

(P1_PROCHOT

and

P2_PROCHOT). Also note, that a strict average of two 8-bit

values may result in Average Px_PROCHOT reflecting a

value that is one LSB lower than the Current Px_PROCHOT

in steady state.

It should be noted that the 8-bit result has a positive bias of

one half of an LSB. This is necessary because a value of 00h

represents that Px_PROCHOT was not asserted at all dur-

ing the sampling window. Any amount of throttling results in

a reading of 01h.

The following table demonstrates the mapping for the 8-bit

result:

8–Bit Result

Percentage Thottled

Exactly 0%

Between 0% and 0.39%

Between 0.39% and 0.78%

Between (n-1)/256 and n/256

253

Between 98.4% and 98.8%

254

Between 98.8% and 99.2%

255

Greater than 99.2%

To achieve the second goal, the LM93 has several compara-

tors that compare the measured percentage reading against

several fixed and 1 variable value. The variable value is user

programmable.

The result of these comparisons generates several error

status bits described in the following table:

Status Description

Comparison Formula

100% Throttle

PROCHOT was never

de-asserted during

monitoring interval.

Greater than or equal to

75% and less than 100%

193

≤ measured value and

not 100%

Greater than or equal to

50% and less than 75%

129

≤ measured value <

193

Greater than or equal to

25% and less than 50%

≤ measured value < 129

Greater than or equal to

12.5% and less than 25%

≤ measured value < 65

Greater than 0% and less

than 12.5%

0 < measured value < 33

Greater than 0%

0 < measured value

Greater than user limit

user limit < measured

value

These status bits are reflected in the PROCHOT Error Sta-

tus

Registers.

Each

the

P1_PROCHOT

and

P2_PROCHOT inputs is monitored independently, and each

has its own set of status registers.

In S3 and S4/5 sleep states, the PROCHOT Monitoring

function does not run. The Current Px_PROCHOT registers

are reset to 00h and the Average Px_PROCHOT registers

hold their current state. Once the sleep state changes back

to S0, the monitoring function is restarted. After the first

PROCHOT measurement has been made, the measure-

ment is written directly into the Current and Average Px-

_PROCHOT registers without performing any averaging. Av-

eraging returns to normal on the second measurement.

12.11 PROCHOT OUTPUT CONTROL

In some cases, it is necessary for the LM93 to drive the

Px_PROCHOT outputs low. There are several conditions

that cause this to happen.

The LM93 can be told to logically short the two PROCHOT

inputs together. When this is done, the LM93 monitors each

of the Px_PROCHOT inputs. If any external device asserts

one of the PROCHOT signals, the LM93 responds by assert-

ing the other PROCHOT signal until the first PROCHOT

signal is de-asserted. This feature should never be enabled

if the PROCHOT signals are already being shorted by an-

other means.

Whenever one of the VRDx_HOT inputs is asserted, the

corresponding Px_PROCHOT pins are asserted by the

LM93. The response time is less than 10 µs. When the

VRDx_HOT input is de-asserted, the Px_PROCHOT pin is

no longer asserted by the LM93. If the LM93 is configured to

short the PROCHOT signals together, it always asserts them

together whenever either of the VRDx_HOT inputs is as-

serted.

Software can manually program the LM93 to drive a PWM

type signal onto P1_PROCHOT or P2_PROCHOT. This is

done via the PROCHOT Override register. See the descrip-

tion of this register for more details. Once again, if the LM93

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