A VME single-board PCM data system that can operate independently in any VMEbus chassis, or replace the 502VA Format Synchronizer to bring the 1502V's advanced features to your Acroamatics TDP

Today's vehicle test operations produce more types and greater volumes of data and transmit it at higher rates and in increasingly complex formats - formats that change in both content and structure. The new Acroamatics programmable single-board PCM decommutator has the processing power and the large working memory to provide the flexibility to decommutate today's and tomorrow's high-speed, dynamically changing PCM formats. And its on-board time, bit synchronizer, and format simulator options make it a one-board PCM telemetry data system, freeing up slots for other uses.

The 1502V Decommutator treats PCM data as a stream of bits divided arbitrarily into packets, each packet representing data values varying in length from 1 to 32 bits. The decommutator uses PCM stream sync patterns to identify the stream data sequence, then tags each packet sequence with a unique ID, regardless of location. The front end of the decommutator

is a pattern correlator that first locates the minor frame sync pattern, then generates control signals to activate a tracking computer operating in sync with the data stream. You program this computer with instructions designed to map a particular PCM format. This map tells the computer how to dissect and identify the serial data sequences forming the PCM stream. You can select the number of bits to extract from the stream for each packet individually, the LSB/MSB data orientation, the output

word MSB/LSB data justification, and how to handle a parity bit. You also assign the ID tag. The decommutator uniquely tags each measurement according to these instructions and outputs a data message containing your ID tag and the stream data. Adding a time tag to this message produces what Acroamatics calls a DIT (Data, ID, Time). Program instructions let you detect bit sequences that are counters or patterns identifying sub-commutated data. You can test data values and decide which sequence of instructions to follow based on the detected data value. Being able to test stream data and store the results for later use gives the decommutator the unique power to handle time-varying PCM formats. You can program the decommutator to process formats in which mainframe lengths, subcommutated sequence lengths, and subcommutated word positions all vary

dynamically, because the decommutator tracking is based on your programmed map of the format. With no bit counter, there is no maximum bit number between sync pattern repetitions, and if the data contains flags to direct the decommutator, a fixed number of bits is not  required. When a format contains only sub-commutated data synchronous to a single additional commutator, you can write the frame out unfolded, as though it were a very long mainframe of fixed sequence. This is not true if there are two or more subframes. The 1502V resolves the resulting asynchronism by providing separate tracking registers for

the mainframe and each of up to six subframes. Since each subframe is independently synchronized by patterns in the data, the decommutator is able to follow maps that vary for each subframe as well as for the mainframe. Each synchronizer can also transfer program control to a point in the map offset by the value of a data word, allowing you to decommutate subframes containing data identified by an ID word embedded in the data. Additional index registers and packet length counters make the

• Frame-synchronizes and decommutates PCM streams from 0bps to 32Mbps.

• Supports up to 4 MBytes of program memory, allowing you to decommutate very complex, time-varying streams without having to reload the format in real-time.

• Assigns arbitrary ID tags in very large PCM formats (more than 131,000 unique data sources in the stream).

• Maintains program compatibility with previous decommutators while removing their program size limitations. Most of your existing 502VA software will run unchanged on the 1502V.

• Assigns word properties and ID tags in a single instruction to speed program execution, and allows you to define word properties within a program region, rather than depending on program flow.

• The 1502V instructions address the entire one-million-instruction program space, removing the previous 4k limitation. This increase removes limitations on program size to make programming larger formats easy.

• Supports up to 16-bit control and subframe ID words. For ID synchronized frames, this means that the major frame may contain as many as 65,536 minor frames. The subframe synchronizers in ID mode can collect up to 16 bits and, in recycle mode, up to 64 bits from non-contiguous locations in the bit stream.

• An enhanced repeat instruction allows a non-incrementing ID tag, permitting easy programming of sequences of a repeated

measurement.

• Control flags manage packet decommutation and data-directed format changes. The expanded capabilities now include set and reset instructions as well as data comparison tests. You can perform data comparisons and bit tests on 32-bit data words.

• Optional mezzanine cards support bit synchronization, IRIG time translation/generation, and format simulation.

• Eight address registers simplify decommutating IRIG-106 Chapter 8 embedded avionics data when you must calculate the output ID tag from data in the stream, a subframe register value, and a base value. This simplifies the complicated task of identifying a particular message based on its identifier in the stream and then sequencing through the message based upon its known structure.

• 16 presettable packet length counters control switching between programs when processing embedded, non-contiguous packet windows in the minor frame.

• 16-bit CRC check for packet telemetry stream error detection.

• The CVT supports real-time display of decommutated PCM data in stand-alone systems that don’t require a data pre-processor or complex data distribution features.

• For applications requiring access to a PCM frame buffer, the 1502V has an on-board double buffer memory that stores minor

frames the host can access directly as a VME bus master.

• The 1502V has a DMA channel that can transfer a stream of decommutated ID-tagged data to the host computer or other VME slave for recording or processing. Systems that do not need data pre-processing or other data distribution functions can implement the complete data system using just the 1502V and its supporting VME host computer. The 1502V does not rely on

the host computer to manage data identification, so the 1502V provides real-time data, remaining coherent to real-time, up to

the full data transfer bandwidth of the system, and is unaffected by host processor workload.

• DMA or memory-mapped data transfers with user-selected record lengths.

• User-programmable message header, including time-of-day stamp, hardware status, record count, and up to three userspecified data words.

• Eleven user-selectable output formats, allowing 16 or 32-bit data words with or without ID tags.