Datasheet

MCP9843/98243
DS22153C-page 16 © 2009 Microchip Technology Inc.
5.1 Registers
The MCP9843/98243 device has several registers that
are user-accessible. These registers include the
Capability register, Configuration register, Event
Temperature Upper-Boundary and Lower-Boundary
Trip registers, Critical Temperature Trip register,
Temperature register, Manufacturer Identification
register and Device Identification register.
The Temperature register is read-only, used to access
the ambient temperature data. The data is loaded in
parallel to this register after t
CONV
. The Event
Temperature Upper-Boundary and Lower-Boundary
Trip registers are read/writes. If the ambient
temperature drifts beyond the user-specified limits, the
MCP9843/98243 device outputs a signal using the
Event pin (refer to Section 5.2.3 “Event Output
Configuration”). In addition, the Critical Temperature
Trip register is used to provide an additional critical
temperature limit.
The Capability register is used to provide bits
describing the MCP9843/98243’s capability in
measurement resolution, measurement range and
device accuracy. The device Configuration register
provides access to configure the MCP9843/98243’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 MCP9843/98243 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 (bits 7-4) need to be cleared or set to ‘0’.
Register 5-1 describes the pointer or the address of
each register.
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 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 7-4 Writable Bits: Write ‘0’’
bit 3-0 Pointer Bits:
0000 = Capability register
0001 = Configuration register (CONFIG)
0010 = Event Temperature Upper-Boundary Trip register (T
UPPER
)
0011 = Event Temperature Lower-Boundary Trip register (T
LOWER
)
0100 = Critical Temperature Trip register (T
CRIT
)
0101 = Temperature register (T
A
)
0110 = Manufacturer ID register
0111 = Device ID/Revision register
1000 = Resolution register
1XXX = Reserved (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.)