MCP9802 Microchip Technology Inc., MCP9802 Datasheet - Page 9

• Manufacturer Part Number: MCP9802
• Description: 2-wire High-accuracy Temperature Sensor
• Manufacturer: Microchip Technology Inc.

4.3
The MCP9800/1/2/3 family has four registers that are
user-accessible. These registers are specified as the
ambient temperature register, the temperature limit-set
register, the temperature hysteresis register and device
configuration registers.
The ambient temperature register is a read-only
register and is used to access the ambient temperature
data. The data from the ADC is loaded in parallel in the
register. The temperature limit-set and temperature
hysteresis registers are read/write registers that
provide user-programmable temperature limits. If the
ambient temperature drifts beyond the programmed
limits, the MCP9800/1/2/3 outputs an alert signal using
the ALERT pin (refer to Section 4.3.4.3 “ALERT Out-
put Configuration”). The device configuration register
provides access for the user to configure the
MCP9800/1/2/3’s various features. These registers are
described in further detail in the following sections.
REGISTER 4-1:
 2004 Microchip Technology Inc.
Registers
bit 7-3
bit 2-0
REGISTER POINTER
Unimplemented: Read as ‘0’
Pointer bits
00 =
01 =
10 =
11 =
Legend:
R = Readable bit
- n = Value at POR
bit 7
U-0
0
Temperature Register
Configuration Register
Temperature Hysteresis Register
Temperature Limit-set Register
U-0
0
U-0
0
W = Writable bit
‘1’ = Bit is set
U-0
0
FIGURE 1:
The registers are accessed by sending register pointer
to the MCP9800/1/2/3 using the serial interface. This is
an 8-bit pointer. However, the two Least Significant bits
(LSb) are used as pointers and all other bits need to be
cleared <0>. This device has additional registers that
are reserved for test and calibration. If these registers
are accessed, the device may not perform according to
the specification. The pointer description is shown
below.
Configuration
Temperature
Register
Register
Register
Register
T
T
HYST
SET
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
U-0
Alert Comp/Int
0
Alert Polarity
Fault Queue
Resolution
Shutdown
One-Shot
MCP9800/1/2/3
Register Block Diagram.
U-0
ALERT Output
0
Control Logic
x = Bit is unknown
R/W-0
P1
DS21909B-page 9
ALERT
Output
R/W-0
P0
bit 0