MCP9808
Section 5.2.3 “Alert Output Configuration”). In
addition, the Critical Temperature Limit register is used
to provide an additional critical temperature limit.
5.1
Registers
The MCP9808 has several registers that are
user-accessible. These registers include the Tempera-
ture register, Configuration register, Temperature Alert
Upper Boundary and Lower Boundary Limit registers,
Critical Temperature Limit register, Manufacturer
Identification register and Device Identification register.
The Configuration register provides access to
configure the MCP9808 device’s various features.
These registers are described in further detail in the
following sections.
The registers are accessed by sending a Register
Pointer to the MCP9808, using the serial interface. This
is an 8-bit write-only pointer. However, the four Least
Significant bits are used as pointers and all unused bits
(Register Pointer<7:4>) need to be cleared or set to ‘0’.
Register 5-1 describes the pointer or the address of
each register.
The Temperature register is read-only, used to access
the ambient temperature data. This register is double-
buffered and it is updated every tCONV. The Temperature
Alert Upper Boundary and Lower Boundary Limit
registers are read/write registers. If the ambient
temperature drifts beyond the user-specified limits, the
MCP9808 outputs a signal using the Alert pin (refer to
REGISTER 5-1:
REGISTER POINTER (WRITE-ONLY)
W-0
—
W-0
—
W-0
—
W-0
—
W-0
W-0
W-0
W-0
Pointer bits
bit 7
bit 0
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
bit 7-4
bit 3-0
W: Writable bits
Write ‘0’.
Bits 7-4 must always be cleared or written to ‘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.
Pointer bits
0000= RFU, Reserved for Future Use (Read-Only register)
0001= Configuration register (CONFIG)
0010= Alert Temperature Upper Boundary Trip register (TUPPER
)
0011= Alert Temperature Lower Boundary Trip register (TLOWER
)
0100= Critical Temperature Trip register (TCRIT
0101= Temperature register (TA)
0110= Manufacturer ID register
0111= Device ID/Revision register
1000= Resolution register
)
1xxx= Reserved(1)
Note 1: Some registers contain calibration codes and should not be accessed.
DS25095A-page 16
© 2011 Microchip Technology Inc.
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