PCI-ASCB

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

PCI-ASCB provides the ability to install one PMC card into a standard PCI slot while providing Dual Redundant ASCB. Types D and Enhanced are supported. The channels 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 that 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. Pn4 IO can be used for Ethernet support via the ASCB 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 RS-485 compliant driver and isolated from the system with a 10/100 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, PCI-ASCB matches the impedance with stub resistors.

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

The PCI bus is interconnected to the PMC via a 32 bit 33 MHz bridge. The bridge allows the PCI bus to operate with different parameters than the PMC card - for example the PCI bus can operate at 66 MHz with 64 bit data and the PMC with 33 mhz and 32 bit data. The buffering within the bridge will take care of the rate and data matching. The local side is set to 33 Mhz based on the ASCB capabilities. The PMC is connected to the bridge with a 32 bit path.

The voltage definitions are buffered between the PCI and PMC buses. The PCI VIO automatically defines the reference levels for the primary side of the bridge. The secondary side of the bridge is set to 3.3V operation for the PMC/prPMC and ASCB functions.

The bridge is located near the PCI "gold fingers" and routed with PCI specification compliant traces for impedance and length to insure that multiple PCI-ASCB cards can be installed onto the same PCI bus stub.

The PCI ±12V, 5V and 3.3V is routed to the PMC slot with voltage planes. High power consumptions PrPMCs are supported. A fan is recommended for high current models.

The PMC JTAG connections are routed to a header. The header is configured to for discrete connections. Add "-JTAG" to your part number for the PMC JTAG header.