lm74a-5-mda National Semiconductor Corporation, lm74a-5-mda Datasheet - Page 9

• Manufacturer Part Number: lm74a-5-mda
• Description: Spi/microwire 12-bit Plus Sign Temperature Sensor Lm74 In Die Form
• Manufacturer: National Semiconductor Corporation

1.0 Functional Description
1.5 INTERNAL REGISTER STRUCTURE
The LM74A has three registers, the temperature register, the configuration register and the manufacturer’s/device identification
register. The temperature and manufacturer’s/device identification registers are read only. The configuration register is write only.
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 LM74A 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: Undefined. TRI-STATE will be output on SI/0.
D2: Always set high.
D3–D15: Temperature Data. One LSB = 0.0625˚C. Two’s complement format.
1.5.3 Manufacturer’s/Device Id Register
D0–D1: Undefined. TRI-STATE will be output on SI/0.
D2–D15: Manufacturer’s/Device ID Data. This register is accessed whenever the LM74A is in shutdown mode.
(Write Only):
(Read Only):
(Read Only):
MSB
D15
D15
D15
X
1
Bit 11 Bit 10
D14
D14
D14
X
0
D13
D13
D13
X
0
Bit 9
D12
D12
D12
X
0
Bit 8
D11
D11
D11
X
0
Bit 7
D10
D10
D10
X
0
(Continued)
Bit 6
D9
D9
D9
X
0
Bit 5
D8
D8
D8
X
0
9
Bit 4
D7
D7
D7
0
Bit 3
D6
D6
D6
0
Bit 2
D5
D5
D5
0
Bit 1
D4
D4
D4
Shutdown
0
LSB
D3
D3
D3
0
D2
D2
D2
1
0
D1
D1
D1
X
X
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D0
D0
D0
X
X