Multichannel Remote/Local
Temperature Sensors
MAX1668/MAX1805/MAX1989
†
level sensitive). Successful reading of the alert
response address clears the interrupt latch.
Command Byte Functions
The 8-bit command byte register (Table 4) is the master
index that points to the various other registers within the
MAX1668/MAX1805/MAX1989. The register’s POR
state is 0000 0000, so that a receive byte transmission
(a protocol that lacks the command byte) that occurs
immediately after POR returns the current local temper-
ature data.
Table 4. Command Byte Bit Assignments for MAX1668/MAX1805/MAX1989
REGISTER
RIT
RET1
RET2
RET3**
RET4**
RS1
RS2
RC
RIHL
RILL
REHL1
RELL1
REHL2
RELL2
REHL3**
RELL3**
REHL4**
RELL4**
WC
WIHL
WILL
WEHI1
WELL1
WEHI2
WELL2
WEHI3**
WELL3**
WEHI4**
WELL4**
MFG ID
DEV ID
COMMAND
00h
01h
02h
03h
04h
05h
06h
07h
08h
09h
0Ah
0Bh
0Ch
0Dh
0Eh
0Fh
10h
11h
12h
13h
14h
15h
16h
17h
18h
19h
1Ah
1Bh
1Ch
FEh
FFh
POR STATE
0000 0000*
0000 0000*
0000 0000*
0000 0000*
0000 0000*
0000 0000
0000 0000
0000 0000
0111 1111
1100 1001
0111 1111
(0110 1110)
1100 1001
0111 1111
1100 1001
0111 1111
1100 1001
0111 1111
1100 1001
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
N/A
0100 1101
0000 0011 (0000 0101)
[0000 1011]
FUNCTION
Read local temperature
Read remote DX1 temperature
Read remote DX2 temperature
Read remote DX3 temperature
Read remote DX4 temperature
Read status byte 1
Read status byte 2
Read Configuration Byte
Read local T
HIGH
limit
Read local T
LOW
limit
Read remote DX1 T
HIGH
limit (MAX1989)
Read remote DX1 T
LOW
limit
Read remote DX2 T
HIGH
limit
Read remote DX2 T
LOW
limit
Read remote DX3 T
HIGH
limit
Read remote DX3 T
LOW
limit
Read remote DX4 T
HIGH
limit
Read remote DX4 T
LOW
limit
Write configuration byte
Write local T
HIGH
limit
Write local T
LOW
limit
Write remote DX1 T
HIGH
limit
Write remote DX1 T
LOW
limit
Write remote DX2 T
HIGH
limit
Write remote DX2 T
LOW
limit
Write remote DX3 T
HIGH
limit
Write remote DX3 T
LOW
limit
Write remote DX4 T
HIGH
limit
Write remote DX4 T
LOW
limit
Read manufacture ID
Read device ID (for MAX1805) [for MAX1989]
*If
the device is in hardware standby mode at POR, all temperature registers read 0°C.
**Not
available for MAX1805.
12
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