lm71cisdx National Semiconductor Corporation, lm71cisdx Datasheet - Page 9

• Manufacturer Part Number: lm71cisdx
• Description: Spi/microwire 13-bit Plus Sign Temperature Sensor
• Manufacturer: National Semiconductor Corporation

1.0 Functional Description
1.3 TEMPERATURE DATA FORMAT
Temperature data is represented by a 14-bit, two’s comple-
ment word with an LSB (Least Significant Bit) equal to
0.03125˚C:
The first data byte is the most significant byte with most
significant bit first, permitting only as much data as neces-
1.5.1 Configuration Register
(Selects shutdown or continuous conversion modes):
D0–D15 set to XX FF hex enables shutdown mode.
D0–D15 set to 00 00 hex sets Continuous conversion mode.
Note: setting D0-D15 to any other values may place the LM70 into a manufacturer’s test mode, upon which the LM71 will stop
responding as described. These test modes are to be used for National Semiconductor production testing only. See Section 1.2
Serial Bus Interface for a complete discussion.
1.5.2 Temperature Register
D0–D1: Logic 1 will be output on SI/0.
D2–D15: Temperature Data. One LSB = 0.03125˚C. Two’s complement format.
1.5.3 Manufacturer/Device ID Register
D0–D1: Logic 1 will be output on SI/0.
D2–D15: Manufacturer’s/Device ID Data. This register is accessed whenever the LM71 is in shutdown mode.
(Write Only):
(Read Only):
(Read Only):
MSB
Temperature
D15
D15
D15
+0.03125˚C
−0.03125˚C
X
1
+150˚C
+125˚C
+25˚C
−25˚C
−40˚C
0˚C
Bit 12 Bit 11 Bit 10
D14
D14
D14
X
0
D13
D13
D13
X
0
0100 1011 0000 0011
0000 1100 1000 0011
0000 0000 0000 0111
0000 0000 0000 0011
0011 1110 1000 0011
1110 1100 0000 0011
1111 0011 1000 0011
1111 1111 1111 1111
D12
D12
D12
Binary
X
0
Digital Output
Bit 9
D11
D11
D11
X
0
Bit 8
D10
D10
D10
X
0
(Continued)
EC03
0C83
FFFF
4B03
3E83
0007
0003
F383
Hex
Bit 7
D9
D9
D9
X
0
Bit 6
D8
D8
D8
X
0
9
Bit 5
D7
D7
D7
sary to be read to determine temperature condition. For
instance, if the first four bits of the temperature data indicate
an overtemperature condition, the host processor could im-
mediately take action to remedy the excessive tempera-
tures.
1.4 SHUTDOWN MODE/MANUFACTURER’S ID
Shutdown mode is enabled by writing XX FF to the LM71 as
shown in Figure 7c. The serial bus is still active when the
LM71 is in shutdown. When in shutdown mode the LM71
always will output 1000 0000 0000 1111. This is the
manufacturer’s/Device ID information. The first 5-bits of the
field (1000 0XXX) are reserved for manufacturer’s ID.
1.5 INTERNAL REGISTER STRUCTURE
The LM71 has three registers, the temperature register, the
configuration register and the manufacturer’s/device identifi-
cation register. The temperature and manufacturer’s/device
identification registers are read only. The configuration reg-
ister is write only.
0
Bit 4
D6
D6
D6
0
Bit 3
D5
D5
D5
0
Bit 2
D4
D4
D4
Shutdown
0
Bit1
D3
D3
D3
1
LSB
D2
D2
D2
1
D1
D1
D1
1
1
www.national.com
D0
D0
D0
1
1