tcn75a Microchip Technology Inc., tcn75a Datasheet - Page 11

• Manufacturer Part Number: tcn75a
• Description: 2-wire Serial Temperature Sensor
• Manufacturer: Microchip Technology Inc.

5.3
The TCN75A has four registers that are user-accessi-
ble. These registers are specified as the Ambient
Temperature (T
(T
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
pointers 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.
REGISTER 5-1:
© 2006 Microchip Technology Inc.
bit 7
Legend:
R = Readable bit
-n = Value at POR
bit 7-3
bit 2-0
.
SET
) register, the Temperature Hysteresis (T
U-0
0
Registers
A
Unimplemented: Read as ‘0’
Pointer bits
00 = Temperature register (T
01 = Configuration register (CONFIG)
10 = Temperature Hysteresis register (T
11 = Temperature Limit-set register (T
) register, the Temperature Limit-set
U-0
0
REGISTER POINTER
W = Writable bit
‘1’ = Bit is set
U-0
0
A
)
HYST
U-0
0
)
SET
HYST
)
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
)
FIGURE 4-2:
U-0
0
Configuration
Temperature
Register
Register
Register
Register
T
T
HYST
SET
Alert Comp/Int
Alert Polarity
Fault Queue
Resolution
Shutdown
One-Shot
U-0
0
Register Block Diagram.
ALERT Output
Control Logic
x = Bit is unknown
R/W-0
P1
TCN75A
DS21935C-page 11
R/W-0
ALERT
Output
P0
bit 0