MAX6657/MAX6658/MAX6659
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.
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
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.
12 ______________________________________________________________________________________
REGISTER ADDRESS POR STATE FUNCTION
RLTS 00h 0000 0000 Read Internal Temperature
RRTE 01h 0000 0000 Read External Temperature
RSL 02h 1000 0000 Read Status Register
RCL 03h 0010 0000 Read Configuration Byte
RCRA 04h 0000 1000 Read Conversion Rate Byte
RLHN 05h 0100 0110 Read Internal High Limit
RLLI 06h 1100 1001 Read Internal Low Limit
RRHI 07h 0100 0110 Read External High Limit
RRLS 08h 1100 1001 Read External Low Limit
WCA 09h 0010 0000 Write Configuration Byte
WCRW 0Ah 0000 1000 Write Conversion Rate Byte
WLHO 0Bh 0100 0110 Write Internal High Limit
WLLM 0Ch 1100 1001 Write Internal Low Limit
WRHA 0Dh 0100 0110 Write External High Limit
WRLN 0Eh 1100 1001 Write External Low Limit
OSHT 0Fh N/A One Shot
REET 10h 0000 0000 Read External Extended Temperature
RIET 11h 0000 0000 Read Internal Extended Temperature
RWO2E 16h 0101 0101 Read/Write External OVERT2 Limit (MAX6659 only)
RW02I 17h 0101 0101 Read/Write Internal OVERT2 Limit (MAX6659 only)
RWOE 19h 0101 0101 Read/Write External OVERT1 Limit
RWOI 20h 0101 0101 Read/Write Internal OVERT1 Limit
HYST 21h 0000 1010 Overtemperature Hysteresis
— FEh 4Dh Read Manufacture ID
Table 4. Command Byte Register Assignments
±1°C, SMBus-Compatible Remote/Local Temperature
Sensors with Overtemperature Alarms
(19 Seiten)
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