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NCT214
http://onsemi.com
11
Table 5. Status Register Bit Assignments
Bit
Name
Function
7
BUSY
1 when ADC is converting
6
LHIGH
1 when local high temperature limit is
tripped
5
LLOW
1 when local low temperature limit is
tripped
4
RHIGH
1 when remote high temperature limit is
tripped
3
RLOW
1 when remote low temperature limit is
tripped
2
OPEN
1 when remote sensor is an open circuit
1
RTHRM
1 when remote THERM limit is tripped
0
LTHRM
1 when local THERM limit is tripped
1. These flags stay high until the status register is read or they
are reset by POR unless Pin 6 is configured as THERM2.
Then, only Bit 2 remains high until the status register is read
or is reset by POR.
Offset Register
Offset errors can be introduced into the remote
temperature measurement by clock noise or when the
thermal diode is located away from the hot spot. To achieve
the specified accuracy on this channel, these offsets must be
removed.
The offset value is stored as a 10bit, twos complement
value in Register 0x11 (high byte) and Register 0x12 (low
byte, left justified). Only the upper two bits of Register 0x12
are used. The MSB of Register 0x11 is the sign bit. The
minimum, programmable offset is 128
°C, and the
maximum is +127.75
°C. The value in the offset register is
added to, or subtracted from, the measured value of the
remote temperature.
The offset register powers up with a default value of 0
°C
and has no effect unless the user writes a different value to it.
Table 6. Sample Offset Register Codes
Offset Value
0x11
0x12
128°C
1000 0000
00 00 0000
4°C
1111 1100
00 00 0000
1°C
1111 1111
00 000000
0.25°C
1111 1111
10 00 0000
0°C
0000 0000
00 00 0000
+0.25°C
0000 0000
01 00 0000
+1°C
0000 0001
00 00 0000
+4°C
0000 0100
00 00 0000
+127.75°C
0111 1111
11 00 0000
OneShot Register
The oneshot register is used to initiate a conversion and
comparison cycle when the NCT214 is in standby mode,
after which the device returns to standby. Writing to the
oneshot register address (0x0F) causes the NCT214 to
perform a conversion and comparison on both the internal
and the external temperature channels. This is not a data
register as such, and it is the write operation to Address 0x0F
that causes the oneshot conversion. The data written to this
address is irrelevant and is not stored.
Consecutive ALERT Register
The value written to this register determines how many
outoflimit measurements must occur before an ALERT is
generated. The default value is that one outoflimit
measurement generates an ALERT. The maximum value that
can be chosen is 4. The purpose of this register is to allow the
user to perform some filtering of the output. This is
particularly useful at the fastest three conversion rates, where
no averaging takes place. This register is at Address 0x22.
Table 7. Consecutive ALERT Register Codes
Register Value
Number of OutofLimit
Measurements Required
yxxx 000x
1
yxxx 001x
2
yxxx 011x
3
yxxx 111x
4
NOTE: x = don’t care bits, and y = SMBus timeout bit.
Default = 0. See SMBus section for more information.