C-compatible serial interface – Rainbow Electronics MAX6635 User Manual
Page 7
The Configuration register is 8 bits, read/write, and
contains the SMBus timeout disable bit, fault queue
enable bit, the temperature alarm output polarity select
bits, the interrupt mode select bit, and the shutdown
bit. Registers T
HIGH
and T
LOW
are 16 bits, read/write,
and contain the values that trigger
ALERT. Register
T
HYST
is 16 bits, read/write, and contains the values by
which the temperature must rise or fall beyond T
HIGH
or
T
LOW
, before
ALERT deasserts.
Control Registers (MAX6635)
Seven registers control the operation of the MAX6635
(Figure 7 and Tables 2 through 7). The Pointer register
is the first addressed and determines which of the other
six registers is acted upon. The other six are the
Temperature, Configuration, High-Temperature
(T
HIGH
), Low-Temperature (T
LOW
), Maximum
Temperature (T
MAX
), and Hysteresis (T
HYST
) registers.
The temperature value is stored as 12 bits plus a sign
bit, read only, and contains the latest temperature data.
The true register length is 16 bits, with the lower three
used as status bits. The digital temperature data con-
tained in the temperature register is in °C, using a
two’s-complement format with 1LSB corresponding to
0.0625°C.
The Configuration register is 8 bits, read/write, and
contains the SMBus timeout disable bit, fault queue
enable bit, the temperature alarm output polarity select
bits, the interrupt mode select bit, and the shutdown
MAX6633/MAX6634/MAX6635
12-Bit Plus Sign Temperature Sensors with
SMBus/I
2
C-Compatible Serial Interface
_______________________________________________________________________________________
7
Figure 3. SMBus Read Timing Diagram
SMBCLK
A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
A
B
C
D
E
F
G
H
I
J
SMBDATA
t
SU:STA
t
HD:STA
t
LOW
t
HIGH
t
SU:DAT
K
L
M
t
SU:STO
t
BUF
E = SLAVE PULLS SMBDATA LINE LOW
F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO MASTER
H = LSB OF DATA CLOCKED INTO MASTER
I = MASTER PULLS DATA LINE LOW
J = ACKNOWLEDGE CLOCKED INTO SLAVE
K = ACKNOWLEDGE CLEAR PULSE
L = STOP CONDITION, DATA
EXECUTED BY SLAVE
M = NEW START CONDITION
0.25s ADC CONVERSION TIME
MAX6633/MAX6634/MAX6635
CONVERSION PERIOD 0.5s
MAX6633/MAX6634/MAX6635
Figure 4. ADC Conversion Timing Diagram
12 BIT + SIGN
ADC
V
CC
CONFIGURATION
TEMPERATURE
SMBus INTERFACE
SDA
SCL
A0
A1
A2
A3
Figure 5. MAX6633 Functional Diagram