PC87366 datasheet(179/240 Pages) NSC

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11.0 Voltage Level Monitor (VLM) (Continued)

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The ALARM output is used to indicate to the system that a voltage outside the high/low limits was detected. The ALARM

output Enable bit in the VCHCFST register, enables the ALARM output to be active when the “Channel High Limit Exceeded”

or the “Channel Low Limit Exceeded” status bit in the VCHCFST register is set.

The SMI output generates an interrupt if any enabled SMI event occurs. Each bit in the VEVSTS0/1 register has a corre-

sponding SMI Enable bit in the VEVSMI0/1 register. When any status bit and its corresponding SMI Enable bit are set the

SMI output is active.

The IRQ output generates an interrupt if any enabled IRQ event occurs. Each bit in the VEVSTS0/1 register has a corre-

sponding IRQ Enable bit in the VEVIRQ0/1 register. When any status bit and its corresponding IRQ Enable bit are set the

IRQ output is active.

Alarm Response Read Sequence

When the VLM activates the ALARM output, the host should respond by reading the VEVSTS0 and VEVSTS1 registers. It

should then access the register of each of the channels whose bit is set in the VEVSTS0 and VEVSTS1 registers and clear

these bits by writing 1 to each of them.

11.2.2

Thermistor-Based Temperature Measurement, Channels 11 to 13

The VLM module can measure environmental temperature by using thermistors. This feature is supported over channels 11

to 13. The temperature measurement under this scheme is based on a voltage divider between AVDD and AVSS where one

of the two resistors is a thermistor. See Figure 36.

The translation of voltage to temperature is determined by the parameters of the thermistor in use. The values in the registers

with the results and limts are defined by the result of the voltage measurement. For the channels that support temperature

measurement, standard temperature monitoring functions are provided: low and high temperature ALERT, and overtemper-

ature shutdown.

11.2.3

VOS, VHIGH and VLOW Limits, OTS and ALERT Output, IRQ and SMI

The voltage reading is compared to three limits: VOS,VHIGH and VLOW. If the voltage reading is outside any of these limits,

the respective status bit (Channel Overtemperature Limit Exceeded, Channel High Limit Exceeded or the Channel Low Limit

Exceeded) in the VCHCFST register is set. The status bit will stay active until it is cleared by the software. An ALERT status

bit in the VEVSTS0/1 register is set when the Channel High Limit Exceeded, the Channel Low Limit Exceeded or the Over-

temperature Event bit for the respective channel is set.

The OTS output is used to indicate to the system that the overtemperature limit has been exceeded. The OTS Output Enable

bit in the VCHCFST register, enables the OTS output to be active when the OTS status of the channel is active.

The ALERT output is used to indicate to the system that the current temperature is outside the high/low limits . The ALERT

output Enable bit in the VTCHCFST register, enables the ALERT output to be active when the “Channel High Limit Exceed-

ed” or the “Channel Low Limit Exceeded” status bit in the VCHCFST register is set. [This signal is not connected in the 365

and 366.]

The SMI output generates an interrupt if any enabled SMI event occurs. Each bit in the VEVSTS1 register has a correspond-

ing SMI Enable bit in the VEVSMI1 register. When any status bit and its corresponding SMI Enable bit are set the SMI output

is active.

The IRQ output generates an interrupt if any enabled IRQ event occurs. Each bit in the VEVSTS1 register has a correspond-

ing IRQ Enable bit in the VEVIRQ1 register. When any status bit and its corresponding IRQ Enable bit are set the IRQ output

is active.

Figure 36. Measuring Temperature using Thermistors

AVDD

NTS

TSi

PTS

TSi

AVDD

AVSS

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