Datasheet

MAX7500–MAX7504
Digital Temperature Sensors and Thermal
Watchdog with Bus Lockup Protection
_______________________________________________________________________________________ 5
I
2
C-Compatible Bus Interface
From a software perspective, the MAX7500–MAX7504
appear as a set of byte-wide registers that contain tem-
perature data, alarm threshold values, and control bits.
A standard I
2
C-compatible 2-wire serial interface reads
temperature data and writes control bits and alarm
threshold data. Each device responds to its own I
2
C
slave address, which is selected using A0, A1, and A2.
See Table 1.
The MAX7500–MAX7504 employ four standard I
2
C
protocols: write byte, read byte, send byte, and receive
byte (Figures 1, 2, and 3). The shorter receive byte pro-
tocol allows quicker transfers, provided that the correct
data register was previously selected by a read-byte
instruction. Use caution when using the shorter proto-
cols in multimaster systems, as a second master could
overwrite the command byte without informing the first
master. The MAX7500 has eight different slave
addresses available; therefore, a maximum of eight
MAX7500 devices can share the same bus. The
MAX7501–MAX7504 each have four different slave
addresses available.
DEVICE BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
MAX7500 1 0 0 1 A2 A1 A0 RD/W
MAX7501 1 0 0 1 1 A1 A0 RD/W
MAX7502 1 0 0 1 0 A1 A0 RD/W
MAX7503 1 0 0 1 1 A1 A0 RD/W
MAX7504 1 0 0 1 0 A1 A0 RD/W
Table 1. I
2
C Slave Addresses
t
BUF
t
SU:STO
t
HD:STA
t
SU:STA
t
HD:DAT
t
HIGH
t
LOW
t
SU:DAT
t
HD:STA
SCL
SDA
t
F
t
R
ACKNOWLEDGE
(A)
STOP
CONDITION
(P)
START
CONDITION
(S)
START
CONDITION
(S)
REPEATED START
CONDITION
(SR)
PARAMETERS ARE MEASURED FROM 10% TO 90%.
Figure 1. Serial Bus Timing