Digilent 410-221P - Manual (Page 2)

PmodTMP2 Reference Manual
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I
2
C Address Selection
The PmodTMP2 I
2 C bus can be set to use one
of four valid addresses. The top five bits of the
address are fixed, and the two least significant
bits are taken from the jumper states of JP2
and JP1. JP2 corresponds to bit one of the
address while JP1 corresponds to bit zero. An
open jumper corresponds to a one in the
address while a shorted jumper corresponds to
a zero. For example, when JP2 and JP1 are
open the device uses the address 0x4B
(0b1001011).
Open Drain Outputs
The PmodTMP2 provides two open drain
output headers for controlling external devices
based upon current temperature thresholds. If
the temperature leaves a range defined by
registers T
LOW
(0x06:0x07) and T
HIGH
(0x04:0x05) then the INT pin on J3 can be
driven low or high based upon the
configuration of the device. Similarly, the CT
pin on J2 can be driven low or high if the
temperature exceeds a critical threshold
defined in T
CRIT
(0x08:0x09). Both of these pins
are pulled up by 10KOhm resistors when they
are not driven by the device. For details on
their electrical specifications and configuration
of the INT and CT pins please refer to the
ADT7420 datasheet.
Quickstart Operation
When the PmodTMP2 is powered up, the
onboard ADT7420 is in a mode that can be
used as a simple temperature sensor without
any initial configuration. By default, the device
address register points to the temperature
MSB register, so a two byte read without
specifying a register will read the value of the
temperature register from the device. The first
byte read back will be the most significant byte
(MSB) of the temperature data, and the second
will be the least significant byte (LSB) of the
data. These two bytes form a two’s
complement 16-bit integer, if the result is
shifted to the right three bits and multiplied by
0.0625 the resulting signed floating point value
will be a temperature reading in degrees
Celsius.
For information on reading and writing to the
other registers of the device, as well as notes
on the accuracy of the temperature
measurements please refer to the ADT7420
datasheet.
Addresses
JP2
JP1 Address
Open Open 0x4B (0b1001011)
Open Shorted 0x4A (0b1001010)
Shorted Open 0x49 (0b1001001)
Shorted Shorted 0x48 (0b1001000)