11

TCM1617

TCM1617-1 2/5/99

 2001 Microchip Technology Inc.

DS21485A

SMBus Thermal Sensor with External Diode Input

Temperature Registers, 8-Bits, Read-Only

(INT_TEMP, EXT_TEMP)

The binary value (2’s complement format) in these two

registers represents temperature of the internal and external

sensors following a conversion cycle. The registers are

automatically updated in an alternating manner.

Internal Temperature Register (INT_TEMP)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

External Temperature Register (EXT_TEMP)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

Temperature Threshold Setpoint Registers,

8-Bits, Read-Write (INT_HLIM, INT_LLIM,

EXT_HLIM, EXT_LLIM)

These registers store the values of the upper and lower

temperature setpoints for event detection. The value is in

2’s-complement binary. INT_HLIM and INT_LLIM are com-

pared with the INT_TEMP value, and EXT_HLIM and

EXT_LLIM are compared with EXT_TEMP. These registers

may be written at any time.

Internal High Limit Setpoint Register (INT_HLIM)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

Internal Low Limit Setpoint Register (INT_LLIM)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

External High Limit Setpoint Register (EXT_HLIM)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

External Low Limit Setpoint Register (EXT_LLIM)

D[7]

D[6]

D[5]

D[4]

D[3]

D[2]

D[1]

D[0]

MSB

x

x

x

x

x

x

LSB

NOTE: POR states:

INT_HLIM

01111111b

+127

°C

INT_LLIM

11001001b

–55

°C

EXT_HLIM

01111111b

+127

°C

EXT_LLIM

11001001b

–55

°C

In the two temperature data and four threshold setpoint

registers, each unit value represents one degree (Celsius).

The value is in 2’s-complement binary format such that a

reading of 00000000b corresponds to 0

°C. Examples of this

temperature-to-binary value relationship are shown in the

following table.

Temperature-to-Digital Value Conversion

(INT_TEMP, EXT_TEMP, INT_HLIM, INT_LLIM,

EXT_HLIM, EXT_LLIM)

Actual

Rounded

Binary

Hex

Temperature

Temperature

Value

Value

+130.00

°C

+127

°C

01111111

7F

+127.00

°C

+127

°C

01111111

7F

+126.50

°C

+127

°C

01111111

7F

+25.25

°C

+25

°C

00011001

19

+0.50

°C+1°C

00000001

01

+0.25

°C0°C

00000000

00

0.00

°C0°C

00000000

00

–0.25

°C0°C

00000000

00

–0.50

°C0°C

00000000

00

–0.75

°C

–1

°C

11111111

FF

–1.00

°C

–1

°C

11111111

FF

–25.00

°C

–25

°C

11100111

E7

–25.25

°C

–25

°C

11100110

E7

–54.75

°C

–55

°C

11001001

C9

–55.00

°C

–55

°C

11001001

C9

–65.00

°C

–65

°C

10111111

BF