SIM225 Technical Reference Manual
41
© Serious Integrated, Inc.
SIM225_TRM_A1ENUS
Revision A1
The temperature sensor is an I2C device on the RX MCU’s RIIC1 port and shares an I2C connection with
the
EEPROM
chip. The temperature sensor
A[2:0]
address bits are hard coded on the module to
000
which results in an I2C address
A[6:0]
of
0x48.
Signal Name
Description
TS
Pin
TS
Name
MCU
Name
RX_SDA1
I2C Serial Data
1
SDA1
P20/SDA1
RX_SCL1
I2C Serial Clock
2
SCL1
P21/SCL1
TEMP_ALERT
Temperature Alert Signal
3
ALERT
P45/IRQ13
The sensor’s
TEMP_ALERT
signal is connected to MCU pin
P45/IRQ13
, and the
TEMP_ALERT
signal can
be programmed on the sensor to signal the MCU when a programmed temperature limit has been
exceeded.
See
the datasheet
for more hardware specifications and programming information.
CLOCKS, OSCILLATORS, AND TIME KEEPING
The following terms are important to understand theory of operation described herein:
Clock:
A square-wave logic-level periodic signal (not a clock as in a timekeeping clock of
time/date/minutes/hours, etc.)
Oscillator:
A crystal or resonating oscillator circuit that creates a fixed-frequency sine wave used in a
specific circuit to create a clock signal
RTCC:
A real time clock/calendar which keeps track of the correct time/date as set by the end user
or some other means.
There are many producers and consumers of stable clock signals (or “clocks”) on the SIM225.
All clocks – including, for instance, the 96MHz CPU core clock, the 12MHz USB clock, and a 9,600baud
serial port clock – can be traced back to an originating oscillator source somewhere. The two main
oscillators/clocks in the SIM225 are:
1)
The relatively accurate 32.768 KHz crystal oscillator attached to the RTCC input on the MCU. For
modules with battery-backed RTCC capability, this oscillator can continue to operate without
module main power applied.
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