Datasheet

MCP9808
DS25095A-page 22 © 2011 Microchip Technology Inc.
5.1.2 UPPER/LOWER/CRITICAL
TEMPERATURE LIMIT REGISTERS
(T
UPPER
/T
LOWER
/T
CRIT
)
The MCP9808 has a 16-bit read/write Alert Output
Temperature Upper Boundary register (T
UPPER
), a 16-bit
Lower Boundary register (T
LOWER
) and a 16-bit Critical
Boundary register (T
CRIT
) that contain 11-bit data in
two’s complement format (0.25°C). This data represents
the maximum and minimum temperature boundary or
temperature window that can be used to monitor
ambient temperature. If this feature is enabled
(Section 5.1.1 “Sensor Configuration Register
(CONFIG)”) and the ambient temperature exceeds the
specified boundary or window, the MCP9808 asserts an
Alert output. (Refer to Section 5.2.3 “Alert Output
Configuration”).
REGISTER 5-3: T
UPPER
/T
LOWER
/T
CRIT
UPPER/LOWER/CRITICAL TEMPERATURE LIMIT REGISTER
(→ ADDRESS ‘0000 0010’b/‘0000 0011’b/‘0000 0100’b)
(1)
U-0 U-0 U-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
— — —Sign2
7
°C 2
6
°C 2
5
°C 2
4
°C
bit 15 bit 8
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 U-0 U-0
2
3
°C 2
2
°C 2
1
°C 2
0
°C 2
-1
°C 2
-2
°C — —
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 15-13 Unimplemented: Read as ‘0’
bit 12 Sign: Sign bit
0 =T
A
≥ 0°C
1 =T
A
< 0°C
bit 11-2 T
UPPER
/T
LOWER
/T
CRIT
: Temperature Boundary bits
Temperature boundary trip data in two’s complement format.
bit 1-0 Unimplemented: Read as ‘0’
Note 1: This table shows two 16-bit registers for T
UPPER
, T
LOWER
and T
CRIT
, located at ‘0000 0010b’,
‘0000 0011b’ and ‘0000 0100b’, respectively.