NCT7491RQR2G【PDF 35/80 页】IC REMOTE THERMAL MONITOR 24QSOP

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NCT7491

http://onsemi.com

List of Status Registers

The complete list of status registers is given below along

with their associated mask registers. The definitions for the

status bits for each of the registers can be found in the

SMBALERT pin.

Table 29. STATUS REGISTERS

Status Bits

Status

Address

Mask

Address

Indicates status assertions in re-

gisters 0x41, 0x7E, 0xB6, 0xB7,

0xB8, 0xB9, 0xBA and 0x89.

0x12

Not

applicable

Voltage & Analog temperature

out of limit bits. OOL bit for re-

gister 0x42.

0x41

0x74

Voltage, Fans, Diode Faults.

OOL bit for register 0x43.

0x42

0x75

PECI0 out of limit, PECI COMM/

DATA error, THERM assertion,

DATA error code. OOL bit for re-

gister 0x81.

0x43

0x82

PECI completion code error,

THERM timer error, Generic

COMM error, PECI13 out of lim-

it bits, PCH byte count error, V

out of limit bit.

0x81

0x83

Push register out of limit bits

0x7E

0x7F

SMBus Master NACK errors

0xB6

0xBC

SMBus Master PEC errors

0xB7

0xBD

SMBus Master Timeout errors

0xB8

0xBE

SMBus Master out of limit bits

0xB9

0xBF

SMBus Master Data Invalid errors

0xBA

0xC0

Voltage Monitoring

The NCT7491 has 5 external voltage measurement

channels. It can also measure its own supply voltage, V

The NCT7491 can measure 5 V, 12 V, and 2.5 V supplies,

and the processor core voltage V

CCP

(0 V to 3 V input). The

2.5 V input can be used to monitor a chipset supply voltage

in computer systems. The V

supply voltage measurement

is carried out through the V

pin. The PECI V

voltage

is also measured and is the dedicated reference voltage for

the PECI circuitry.

AnalogtoDigital Converter

All analog inputs are multiplexed into the onchip,

successive approximation, analogtodigital converter.

This has a resolution of 10 bits. The basic input range is 0 V

to 2 V, but the inputs have builtin attenuators to allow

measurement of 2.5 V, 3.3 V, 5 V, 12 V, and the processor

core voltage V

CCP

without any external components. To

allow the tolerance of these supply voltages, the ADC

produces an output of 3/4 full scale (768 dec or 300 hex) for

the nominal input voltage, and so has adequate headroom to

cope with overvoltages.

Voltage Input Circuitry

The internal structure for the analog inputs is shown in

Figure 24. The input circuit consists of an input protection

diode, an attenuator, plus a capacitor to form a firstorder

lowpass filter that gives input immunity to high frequency

noise. The attenuators can be disabled for the voltage

channels, except for the Vcc channel.

12 V

215.7 k

30.2 k

5 V

85.9 k

36.6 k

2.5 V

49.4 k

74 k

Vcc

66.7 k

55.8 k

Vccp

41.1 k

82.3 k

13.7 k

109.7 k

2.6 pF

Mux

Figure 24. Voltage Input Structures

2.6 pF

Voltage Measurement Registers

" Reg. 0x1E, V

Reading = 0x00 default

" Reg. 0x20, 2.5 V Reading = 0x00 default

" Reg. 0x21, V

CCP

Reading = 0x00 default

" Reg. 0x22, V

Reading = 0x00 default

" Reg. 0x23, 5 V Reading = 0x00 default

" Reg. 0x24, 12 V Reading = 0x00 default

Extended Resolution Registers

Voltage measurements can be made with higher accuracy

using the extended resolution registers (0x1F, 0x76 and

0x77). Whenever the extended resolution registers are read,

the corresponding data in the voltage measurement registers

(0x1E, 0x20 to 0x24) is locked until their data is read. That

is, if extended resolution is required, the extended resolution

the appropriate voltage measurement register.

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