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o One USB port.
o One SPI bus for interacting to the Datakey and SD card on Host Board and the RTC on
Engine Board.
o One local I2C bus for interfacing to the Boot EEPROM.
o One BDM bus for allowing the programming.
o Monitors and sets the status of important input/output signals (Powerup, Powerdown,
Linesync, Datakey present, CPU Active, CPU Reset, etc).
2.4.2.4 Reset management
The Engine Board provides an active-low, +5VDC, output signal called CPU_RESET. It is used to reset
other internal/external system devices.
This output signal is generated by the CPU Reset line circuit. This circuit acts as an OR gate that receives
two input signals, both are provided by the Processor, one input signal is related to a hardware reset and
the other one to a software reset.
Hardware Reset
This active-low reset signal is provided by the Processor upon the process of an input signal
representing a reset condition. This reset condition is the output of a two inputs AND gate, one input
signals is POWERUP and the other one is an output from a supervisory circuit.
POWERUP is an active-low Power Supply’s control signal triggered by a long power outage.
The active-low output signal from the supervisory circuit is caused by a low-voltage condition at Vcc.
Software Reset
This active-low reset signal is provided by the Processor upon the process of a reset command from
the application software.
2.4.2.5 Support circuitry
In order for the main sub-systems to operate on the Engine Board, there is support circuitry related to the
functionality such as connectors, buffers, drivers, USB and Ethernet transceivers, programming test ports,
Linesync and ACFail control circuit, Reset circuits, microprocessor supervisory circuit, backup circuit,
memory & peripherals’ power source and CPU’s core power source.
Also there are some special signals related to monitoring, status and control.
50-position Connector Headers
P1 and P2 are two 50-position double row connector headers that are used; they are located properly in
order to be plugged into any Host board meeting this standard.
It has all the necessary connections from all circuitry on Engine board so that they have their
corresponding lines on the Host board.
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