Freescale Semiconductor Tower System Kit TWR-56F8400 TWR-56F8400-KIT TWR-56F8400-KIT Manual Do Utilizador
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TWR-56F8400-KIT
TWR-56F8400 User’s Manual
Page 14 of 35
2.3.6 Tower Elevator Connectors
The TWR-56F8400 board features two expansion card-edge connectors that interface to Elevator
boards in a Tower System: the Primary and Secondary Elevator connectors. The Primary Elevator
connector, comprised of sides A and B, is utilized by the TWR-56F8400 board, while the Secondary
Elevator connector only makes connections to ground (GND). Table 7 in Appendix A – Tower Elevator
Connector Pin Functions lists the pin functions for the Primary Elevator Connector.
boards in a Tower System: the Primary and Secondary Elevator connectors. The Primary Elevator
connector, comprised of sides A and B, is utilized by the TWR-56F8400 board, while the Secondary
Elevator connector only makes connections to ground (GND). Table 7 in Appendix A – Tower Elevator
Connector Pin Functions lists the pin functions for the Primary Elevator Connector.
2.3.7 Thermistors as Analog Inputs
The TWR-56F8400 board provides four thermistors (RT1-4) near the corners of the board that can be
used as single ended or differential analog inputs to the MC56F84789 DSC as can be seen on sheet 6 of
the schematic. In addition to each thermistor there is a resistor between the thermistor and P3_3V and
another resistor between the thermistor and ground. The thermistors are all 10K ohm parts but the
associated divider chain uses different resistors. This makes the voltage across the thermistor larger or
smaller and provides the ability to try the different gain settings on the analog channels. All four
thermistor circuits are designed to provide useable differential inputs over the temperature range of
90˚C to -20˚C. RT2 and RT4 both give a differential voltage of ~1.65V at 25˚C. RT1 gives a differential
voltage of 0.10V and RT3 gives a differential voltage of 0.28V at 25 ˚C.
In addition to the thermistor voltage divider chain each thermistor has a 0.1 uF capacitor in parallel.
Each thermistor circuit also has a header that allows the thermistor to be disconnected from the
analog inputs to the DSC. If a user wishes to apply an external analog value these headers may be
removed and the external analog signal attached to the DSC side of the headers. Finally, each analog
input to the DSC has a 100 ohm series resistor and a 2200 pF capacitor as a low pass filter. This helps
protect the DSC from electrostatic discharges and lowers the impedance of the analog signal so that it
can be sampled with less noise.
used as single ended or differential analog inputs to the MC56F84789 DSC as can be seen on sheet 6 of
the schematic. In addition to each thermistor there is a resistor between the thermistor and P3_3V and
another resistor between the thermistor and ground. The thermistors are all 10K ohm parts but the
associated divider chain uses different resistors. This makes the voltage across the thermistor larger or
smaller and provides the ability to try the different gain settings on the analog channels. All four
thermistor circuits are designed to provide useable differential inputs over the temperature range of
90˚C to -20˚C. RT2 and RT4 both give a differential voltage of ~1.65V at 25˚C. RT1 gives a differential
voltage of 0.10V and RT3 gives a differential voltage of 0.28V at 25 ˚C.
In addition to the thermistor voltage divider chain each thermistor has a 0.1 uF capacitor in parallel.
Each thermistor circuit also has a header that allows the thermistor to be disconnected from the
analog inputs to the DSC. If a user wishes to apply an external analog value these headers may be
removed and the external analog signal attached to the DSC side of the headers. Finally, each analog
input to the DSC has a 100 ohm series resistor and a 2200 pF capacitor as a low pass filter. This helps
protect the DSC from electrostatic discharges and lowers the impedance of the analog signal so that it
can be sampled with less noise.
2.3.8 CAN Transceiver
The TWR-56F8400 board has a CAN transceiver circuit that may be connected to the CAN pins of the
DSC. The CAN transceiver (U503) can be connected to the GPIOC11/CANTX/SCL1/TXD1 and
GPIOC12/CANRX/SDA1/RXD1 pins of the DSC through the header at J16. Installing a shunt from pin 1 to
pin 2 connects the TXD nets and installing a shunt from pin 3 to pin 4 connects the RXD nets. Note that
the GPIOC11/CANTX/SCL1/TXD1 and GPIOC12/CANRX/SDA1/RXD1 nets also go to the primary elevator
edge connector (J500A) pins B41 and B42 and to the Auxiliary connector (J502) pins 15 and 17. When
using these nets for CAN communications care must be taken that these nets are not driven from these
other connectors.
The transceiver is capable of running from 3.3V and is powered by the P3_3V/5V power rail. The
transceiver output is connected to header J13 with CANH connected to pin 4 and CANL connected to
DSC. The CAN transceiver (U503) can be connected to the GPIOC11/CANTX/SCL1/TXD1 and
GPIOC12/CANRX/SDA1/RXD1 pins of the DSC through the header at J16. Installing a shunt from pin 1 to
pin 2 connects the TXD nets and installing a shunt from pin 3 to pin 4 connects the RXD nets. Note that
the GPIOC11/CANTX/SCL1/TXD1 and GPIOC12/CANRX/SDA1/RXD1 nets also go to the primary elevator
edge connector (J500A) pins B41 and B42 and to the Auxiliary connector (J502) pins 15 and 17. When
using these nets for CAN communications care must be taken that these nets are not driven from these
other connectors.
The transceiver is capable of running from 3.3V and is powered by the P3_3V/5V power rail. The
transceiver output is connected to header J13 with CANH connected to pin 4 and CANL connected to