The power and communications module is a printed circuit board (PCB) that has the capability of providing power to an embedded processor and converting Ethernet packets into serial data to transfer to the processor. The purpose of the new design is to address the shortcomings of previous designs, including limited bandwidth and program memory, lack of control over packet processing, and lack of support for timing synchronization.

The module includes an RJ-45 with integrated magnetics and power passthrough, integrated Power over Ethernet (PoE) controller, an Ethernet controller [media access controller (MAC)], a Silicon Laboratories C8051F120 microcontroller with synchronous and asynchronous communication ports, a realtime clock, a hardware watchdog timer, a DC-DC converter with triple output, and 1 Mbit of non-volatile ferroelectric RAM. This new kind of RAM, called FRAM, does not require a battery backup, yet is has unlimited read and write cycles, and a much smaller access time (60 nanoseconds) than traditional flash memory. The FRAM may be used to store data from the C8051.

The new design of the module creates a robust serial-to-Ethernet conversion that is powered using the existing Ethernet cable. Not only can the module perform these conversions, it also has the processing capability and memory to implement other protocols (like IEEE 1451, IEEE 1588, etc.) and to offload these tasks from other embedded processors.

This innovation has a small form factor that allows it to power processors and transducers with minimal space requirements. The power for the module is provided over the spare pins of the Ethernet CAT-5 cable from Power Source Equipment (PSE) according to IEEE 802.11a. The power and communication module then converts the power into three different voltage levels: 5 volts DC, +12 volts DC and –12 volts DC, which are provided to the embedded processor or transducer through a power header on the PCB.

The power and communication module is also equipped with an Ethernet Controller and microprocessor that can send and receive Internet Protocol (IP)- based packets over the CAT-5 cable on a 10/100 Megabit Ethernet network. The Ethernet controller takes care of overhead communication with the network, and the microprocessor is able to access packets stored in the Ethernet controller’s buffer. The microprocessor translates the packets to and from serial data to packets using a standard serial peripheral interface (SPI). The SPI data can be sent and received to another embedded processor over the digital header on the PCB.

The power and communication module is equipped with a hardware watchdog timer that monitors the SPI communication and resets the processors if communications cease. The power and communication module has the additional feature of a real time clock (RTC) that is used to synchronize the time of the power and communication module and its associated embedded processor(s) with the time of another entity on the Ethernet network. Time synchronization is achieved through a combination of hardware and software using the RTC and IEEE 15888 1588 Precision Time Protocol.

This work was done by Jose Perotti of Kennedy Space Center, and Carlos Mata and Rebecca Oostdyk of ASRC Aerospace Corp. For more information, download the Technical Support Package (free white paper) at www.techbriefs.com/tsp under the Electronics/Computers category. KSC-13112