PCIe-ASCB

PCIe-ASCB (Avionics Standard Communications Bus) Bridge based PCIe and PMC Compatible Adapter Carrier with Dual Redundant ASCB Function.

PCIe-ASCB provides the ability to install one PMC card into a standard PCIe slot while providing Dual Redundant ASCB. Types D and Enhanced are supported. The ports are independent allowing any combination of D and Enhanced processing. The primary and redundant do need to use the same protocol. The ASCB design is done within an FPGA to allow for other applications. The current design is Dual Port RAM based with circular buffers implemented to transfer data from the local CPU to the IO port and vice-versa.

The base ASCB design incorporates a master timer used to coordinate when transmissions will take place. The Software communicates with the transmit state-machine via address pointers and bit level commands stored into the RAM. The RAM is split into 4 sections to cover the two receivers and two transmitters. The RAM is managed as a circular buffer with global controls to allow the software to restart from a known location etc. Software can pre-pack messages to be sent and the hardware will automatically wait for the programmed time, then send the packets with proper gap, pre and post ambles plus CRC processing. The interpacket gap defaults to the ethernet standard and is programmable to allow for test.

The PMC slot can be used with a standard Target PMC device or with a PrPMC. The interrupts can be routed [dipswitch option] between the PrPMC and ASCB function or to the PCI host. A PrPMC can be used for local "real time" processing. Please note the PMC bezel is mounted inboard on this carrier. Front panel IO from the PMC will be internal to the PC. Most other Dynamic Engineering carriers have the PMC connector mounted through the PCI bezel.

The ASCB or user function is provided through two DB-9 connectors. Each connector has primary and redundant IO plus disables and a frame marker reference. The signals for transmit originate within the FPGA, are buffered by ASCB compliant driver and isolated from the system with a transformer. On the card side of the transformer a separate receiver is connected with the output routed to the FPGA. ASCB cabling has a 62 ohm impedance, PCIe-ASCB matches the impedance with stub resistors and impedance controlled routing.

Internal same channel loop-back is available including all components except for the transformer. The transmit side has shunts to allow positive isolation for cases where the transmitter must not become activated - for example acting as a "bus snooper". Software also has control over the transmit enable via a master enable, and the state-machine associated with transmission.

For superior performance PCIe-ASCB has a cooling cutout for increased airflow to the PMC. If your installed PMC requires a fan you can order the PCIe-ASCB-FAN to have a fan mounted to your PCIe-ASCB. "Zero Slot Fan"™ technology is used, allowing use with standard PMC heights and legal for single slot PCIe operation.

The PCIe bus is interconnected to the PMC via a 32 bit 33 MHz bridge. The bridge converts between PCIe and PCI to support the PMC and ASCB functions.

The secondary side of the bridge [PCI] is set to 3.3V operation for the PMC/prPMC and ASCB functions.

The bridge is located near the PCIe "gold fingers" and routed with PCIe specification compliant traces for impedance and length to insure proper operation.

The PCIe 12V is converted to 5V, -5V, 3.3V, 1.2V, and -12V to support the PMC and ASCB functions. High power consumptions PrPMC's are supported. A fan is recommended for high current models. The Aux Power Connector is available for higher current situations.

The FPGA JTAG connections are routed to a header. The header is configured for discrete connections. Add "-JTAG" to your part number for the JTAG header. Not needed unless a custom implementation is in use.