Microchip Technology MCP9800DM-DL2 Data Sheet
MCP9800/1/2/3
DS21909D-page 14
2010 Microchip Technology Inc.
5.3
Registers
The MCP9800/1/2/3 has four registers that are
user-accessible. These registers are specified as the
Ambient Temperature (T
user-accessible. These registers are specified as the
Ambient Temperature (T
A
) register, the Temperature
Limit-set (T
SET
) register, the Temperature Hysteresis
(T
HYST
) register and device Configuration (CONFIG)
register.
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
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
). 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.
The registers are accessed by sending Register Point-
ers to the MCP9800/1/2/3 using the serial interface.
This is an 8-bit pointer. However, the two Least
Significant bits (LSbs) are used as pointers and all
other bits need to be cleared <0>. This device has addi-
tional 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.
MCP9800/1/2/3’s various features. These registers are
described in further detail in the following sections.
The registers are accessed by sending Register Point-
ers to the MCP9800/1/2/3 using the serial interface.
This is an 8-bit pointer. However, the two Least
Significant bits (LSbs) are used as pointers and all
other bits need to be cleared <0>. This device has addi-
tional 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.
FIGURE 5-2:
Register Block Diagram.
ALERT Output
Control Logic
ALERT
Output
Resolution
Temperature
T
HYST
T
SET
Register
Register
Register
Configuration
Register
One-Shot
Shutdown
Fault Queue
Alert Polarity
Alert Comp/Int
REGISTER 5-1:
REGISTER POINTER
U-0
U-0
U-0
U-0
U-0
U-0
R/W-0
R/W-0
0
0
0
0
0
0
P1
P0
bit 7
bit 0
Legend:
R = Readable bit
R = Readable bit
W = Writable bit
U = Unimplemented bit, read as ‘0’
-n = Value at POR
‘1’ = Bit is set
‘0’ = Bit is cleared
x = Bit is unknown
bit 7-2
Unimplemented: Read as ‘0’
bit 1-0
Px<1:0>: Pointer bits
00 = Temperature register (T
00 = Temperature register (T
A
)
01 = Configuration register (CONFIG)
10 = Temperature Hysteresis register (T
10 = Temperature Hysteresis register (T
HYST
)
11 = Temperature Limit-set register (T
SET
)
.