TCN75A_1 Datasheet, PDF (14/40 Pages) Microchip Technology – 2-Wire Serial Temperature Sensor

TCN75A
5.3 Registers
The TCN75A has four registers that are
user-accessible. These registers are specified as the
Ambient Temperature (T_A) register, the Temperature
Limit-set (T_SET) register, the Temperature Hysteresis
(T_HYST) register and device Configuration (CONFIG)
register.
The Ambient Temperature register is a read-only
register and is used to access the ambient temperature
data. The data from the ADC is loaded in parallel in the
register. The Temperature Limit-set and Temperature
Hysteresis registers are read/write registers that
provide user-programmable temperature limits. If the
ambient temperature drifts beyond the programmed
limits, the TCN75A outputs an alert signal using the
ALERT pin (refer to Section 5.3.4.3 “ALERT Output
Configuration”). The device Configuration register
provides access for the user to configure the TCN75A’s
various features. These registers are described in
further detail in the following sections.
The registers are accessed by sending Register Point-
ers to the TCN75A using the serial interface. This is an
8-bit pointer. However, the two Least Significant bits
(LSbs) are used as pointers and all other bits need to
be cleared <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. The pointer description
is shown below.
Resolution
One-Shot
Shutdown
Fault Queue
Alert Polarity
Alert Comp/Int
Configuration
Register
Temperature
Register
T_HYST
Register
T_SET
Register
ALERT Output
Control Logic
ALERT
Output
FIGURE 5-2:
Register Block Diagram.
REGISTER 5-1: REGISTER POINTER
U-0
U-0
U-0
U-0
U-0
0
0
0
0
0
bit 7
U-0
R/W-0
R/W-0
0
P1
P0
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 7-2
bit 1-0
.
Unimplemented: Read as ‘0’
Pointer bits
00 = Temperature register (T_A)
01 = Configuration register (CONFIG)
10 = Temperature Hysteresis register (T_HYST)
11 = Temperature Limit-set register (T_SET)
DS21935D-page 14
 2010 Microchip Technology Inc.