Ver: 2.5

Dec 14, 2004

TEL: 886-3-5788833

http://www.gmt.com.tw

8

G767

Global Mixed-mode Technology Inc.

Write Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

DATA

ACK

P

7 bits

8 bits

8 bits

1

Slave Address: equivalent to chip- select line of a 3-wire interface

Command Byte: selects which register you are writing to

Data byte: data goes into the register set by the command byte (to set thresholds, configuration masks, and sam

pling rate)

Read Byte Format

S

ADDRESS WR

ACK

COMMAND

ACK

S

ADDRESS RD

ACK

DATA

///

P

7 bits

8bits

7bits

8 bits

Slave Address: equivalent to chip- select line

Command Byte: selects which register you are reading from

Slave Address: repeated due to change in data-flow direction

Data byte: reads from the register set by the command byte

Send Byte Format

S

ADDRESS

WR

ACK

COMMAND

ACK

P

7 bits

8 bits

Command Byte: sends command with no data , usually used for one-shot command

Receive Byte Format

S

ADDRESS

RD

ACK

DATA

///

P

7 bits

8 bits

Data Byte: reads data from the register commanded by the last Read Byte or Write Byte transmission; also used

for SMBus Alert Response return address

S = Start condition Shaded = Slave transmission P = Stop condition /// = Not acknowledged

Figure 3. SMBus Protocols

Table 2. Data Format (Twos-Complement)

DIGITAL OUTPUT

DATA BITS

TEMP.

(°C)

ROUND

TEMP.

(°C)

SIGN

MSB

LSB

+130.00

+127

0

111

1111

+127.00

+127

0

111

1111

+126.50

+127

0

111

1111

+126.00

+126

0

111

1110

+25.25

+25

0

001

1001

+0.50

+1

0

000

0001

+0.25

+0

0

000

0000

+0.00

+0

0

000

0000

-0.25

+0

0

000

0000

-0.50

+0

0

000

0000

-0.75

-1

1

111

1111

-1.00

-1

1

111

1111

-25.00

-25

1

110

0111

-25.50

-25

1

110

0110

-54.75

-55

1

100

1001

-55.00

-55

1

100

1001

-65.00

-65

1

011

1111

-70.00

-65

1

011

1111

Alarm Threshold Registers

Four registers store alarm threshold data, with

registers for each A/D channel. If either measured

temperature equals or exceeds the corresponding

alarm threshold value, an ALERT interrupt is as-

serted.

is full scale (0111 1111, or +127

°C). The POR state of

Diode Fault Alarm

There is a continuity fault detector at DXP that detects

whether the remote diode has an open-circuit condi-

tion. At the beginning of each conversion, the diode

fault is checked, and the status byte is updated. This

fault detector is a simple voltage detector; if DXP rises

source, a fault is detected. Note that the diode fault

isn’t checked until a conversion is initiated, so immedi-

ately after power-on reset the status byte indicates no

fault is present, even if the diode path is broken.