
Ver 1.3
Oct 28, 2002
TEL: 886-3-5788833
http://www.gmt.com.tw
10
G768B
Global Mixed-mode Technology Inc.
Write Byte Format
S
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
sampling rate)
Address
7 bits
WR
ACK
Command
8 bits
ACK
DATA
8 bits
ACK
P
1
Read Byte Format
S
Address WR
7 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
ACK
Command ACK
8 bits
S
Address
7 bits
RD
ACK
DATA
8 bits
///
P
Send Byte Format
S
Command Byte:
sends command with no data usually used for one-shot command
Address
7 bits
WR
ACK
Command
8 bits
ACK
P
Receive Byte Format
S
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
Address
7 bits
RD
ACK
Data
8 bits
///
P
S = Start condition Shaded = Slave transmission P = Stop condition /// = Not acknowledged
Fig 5. SMBus Protocols
Table 3. Data Format (Twos-Complement)
ROUND
TEMP.
(
°
C)
+130.00
+127
+127.00
+127
+126.50
+127
+126.00
+126
+25.25
+25
+0.50
+1
+0.25
+0
+0.00
+0
-0.25
+0
-0.50
+0
-0.75
-1
-1.00
-1
-25.00
-25
-25.50
-25
-54.75
-55
-55.00
-55
-65.00
-65
-70.00
-65
DIGITAL OUTPUT
DATA BITS
SIGN
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
TEMP.
(
°
C)
MSB
111
111
111
111
001
000
000
000
000
000
111
111
110
110
100
100
011
011
LSB
1111
1111
1111
1110
1001
0001
0000
0000
0000
0000
1111
1111
0111
0110
1001
1001
1111
1111
Alarm Threshold Registers
Four registers store alarm threshold data, with
high-temperature
(THIGH)
(TLOW) registers for each A/D channel. If either
measured temperature equals or exceeds the corre-
sponding alarm threshold value, an ALERT interrupt
is asserted.
and
low-temperature
The power-on-reset (POR) state of both THIGH regis-
ters is full scale (0111 1111, or +127°C). The POR
state of both TLOW registers is 1100 1001 or -55°C.
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
above V
CC
- 1V (typical) due to the diode current
source, a fault is detected. Note that the diode fault
isn't checked until a conversion is initiated, so imme-
diately after power-on reset the status byte indicates
no fault is present, even if the diode path is broken.