±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
MAX6657/MAX6658/MAX6659
Table 4. Command Byte Register Assignments
REGISTER
RLTS
RRTE
RSL
RCL
RCRA
RLHN
RLLI
RRHI
RRLS
WCA
WCRW
WLHO
WLLM
WRHA
WRLN
OSHT
REET
RIET
RWO2E
RW02I
RWOE
RWOI
HYST
—
ADDRESS
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
16h
17h
19h
20h
21h
FEh
POR STATE
0000 0000
0000 0000
1000 0000
0010 0000
0000 1000
0100 0110
1100 1001
0100 0110
1100 1001
0010 0000
0000 1000
0100 0110
1100 1001
0100 0110
1100 1001
N/A
0000 0000
0000 0000
0101 0101
0101 0101
0101 0101
0101 0101
0000 1010
4Dh
Read Internal Temperature
Read External Temperature
Read Status Register
Read Configuration Byte
Read Conversion Rate Byte
Read Internal High Limit
Read Internal Low Limit
Read External High Limit
Read External Low Limit
Write Configuration Byte
Write Conversion Rate Byte
Write Internal High Limit
Write Internal Low Limit
Write External High Limit
Write External Low Limit
One Shot
Read External Extended Temperature
Read Internal Extended Temperature
Read/Write External
OVERT2
Limit (MAX6659 only)
Read/Write Internal
OVERT2
Limit (MAX6659 only)
Read/Write External
OVERT1
Limit
Read/Write Internal
OVERT1
Limit
Overtemperature Hysteresis
Read Manufacture ID
FUNCTION
For example,
OVERT1
has a threshold set to +50°C
and is connected to a fan.
OVERT2
has a threshold of
+75°C and is connected to a system shutdown. If the
system reaches +50°C, the fan turns on, trying to cool
the system. If the system continues to heat up to the
critical temperature of +75°C,
OVERT2
causes the sys-
tem to shut down.
Command Byte Functions
The 8-bit Command Byte register (Table 4) is the master
index that points to the various other registers within the
MAX6657/MAX6658/MAX6659. This register’s POR state
is 0000 0000, so a Receive Byte transmission (a protocol
that lacks the command byte) occurring immediately
after POR returns the current local temperature data.
software standby mode (RUN/STOP bit = 1), a new
conversion is begun, after which the device returns to
standby mode. If a conversion is in progress when a
one-shot command is received, the command is
ignored. If a one-shot command is received in autocon-
vert mode (RUN/STOP bit = 0) between conversions, a
new conversion begins, the conversion rate timer is
reset, and the next automatic conversion takes place
after a full delay elapses.
Configuration Byte Functions
The Configuration Byte register (Table 5) is a Read-Write
register with several functions. Bit 7 is used to mask (dis-
able) interrupts. Bit 6 puts the device into software stand-
by mode (STOP) or autonomous (RUN) mode. Bit 5
selects the type of external junction (set to 1 for a sub-
strate PNP on an IC or set to 0 for a discrete diode-con-
nected transistor) for optimized measurements. Bits 0 to
4 are reserved and return a zero when read.
One-Shot
The one-shot command immediately forces a new con-
version cycle to begin. If the one-shot command is
received when the MAX6657/MAX6658/MAX6659 are in
12
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MAXIM [ MAXIM INTEGRATED PRODUCTS ]
