Datasheet

MCP9843/98243
DS22153C-page 20 © 2009 Microchip Technology Inc.
5.1.2 SENSOR CONFIGURATION
REGISTER (CONFIG)
The MCP9843/98243 device has a 16-bit Configuration
register (CONFIG) that allows the user to set various
functions for a robust temperature monitoring system.
Bits 10 thru 0 are used to select Event output boundary
hysteresis, device Shutdown or Low-Power mode,
temperature boundary and critical temperature lock,
temperature Event output enable/disable. In addition,
the user can select the Event output condition (output
set for T
UPPER
and T
LOWER
temperature boundary or
T
CRIT
only), read Event output status and set Event
output polarity and mode (Comparator Output or
Interrupt Output mode).
The temperature hysteresis bits 10 and 9 can be used
to prevent output chatter when the ambient
temperature gradually changes beyond the user-
specified temperature boundary (see Section 5.2.2
“Temperature Hysteresis (T
HYST
)”. The Continuous
Conversion or Shutdown mode is selected using bit 8.
In Shutdown mode, the band gap temperature sensor
circuit stops converting temperature and the Ambient
Temperature register (T
A
) holds the previous
successfully converted temperature data (see
Section 5.2.1 “Shutdown Mode”). Bits 7 and 6 are
used to lock the user-specified boundaries T
UPPER
,
T
LOWER
and T
CRIT
to prevent an accidental rewrite.
Bits 5 thru 0 are used to configure the temperature
Event output pin. All functions are described in
Register 5-3 (see Section 5.2.3 “Event Output
Configuration”).
REGISTER 5-3: CONFIGURATION REGISTER (CONFIG) → ADDRESS ‘0000 0001’b
U-0 U-0 U-0 U-0 U-0 R/W-0 R/W-0 R/W-0
————— T
HYST
SHDN
bit 15 bit 8
R/W-0 R/W-0 R/W-0 R-0 R/W-0 R/W-0 R/W-0 R/W-0
Crit. Lock Win. Lock Int. Clear Event Stat. Event Cnt. Event Sel. Event Pol. Event Mod.
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 15-11 Unimplemented: Read as ‘0’
bit 10-9 T
UPPER
and T
LOWER
Limit Hysteresis (T
HYST
):
00 = 0°C (power-up default)
01 = 1.5°C
10 = 3.0°C
11 = 6.0°C
(Refer to Section 5.2.3 “Event Output Configuration”)
This bit can not be altered when either of the lock bits are set (bit 6 and bit 7).
This bit can be programmed in shutdown mode.
bit 8 Shutdown Mode (SHDN):
0 = Continuous Conversion (power-up default)
1 = Shutdown (Low-Power mode)
In shutdown, all power-consuming activities are disabled, though all registers can be written to or read.
Event output will de-assert.
This bit cannot be set ‘1’ when either of the lock bits is set (bit 6 and bit 7). However, it can be cleared
‘0’ for Continuous Conversion while locked (Refer to Section 5.2.1 “Shutdown Mode”).