The ATT PIM1553MT is a single channel dual redundant Mil-Std-1553 and STANAG-3838 Bus Monitor Protocol Interface Module (PIM) designed to be fitted onto the ATT-DAS PC/16 test and simulation card for PC/AT compatible computers.

This module occupies two of the 8 sites on the ATT-DAS PC/16. A single host card can accept up to 2 1553MT PIMs. At present the PIM1553MT cannot be mounted on a motherboard containing other types of PIM. However, other motherboards in the same system could contain additional PIM types

To allow much larger systems to be constructed, it is possible to install up to 15 ATT-DAS PC/16 cards into a single PC backplane. Each card could contain two 1553MT PIMs, and so systems containing up to 30 Mil-Std-1553 channels can be built.

The PIM1553MT uses two Bus Isolation Transformers to connect to the Mil-Std-1553 bus, one for each of the Dual Redundant Busses. This provides maximum isolation for both the unit under test, and the host PC. The outputs from the transformers are fed via line receiver chips to a custom logic array.

The PIM1553MT’s LCA receives and decodes the incoming messages. It can detect which of the two dual redundant busses the data was received on, and Sync, Manchester or Parity encoding errors that exist on a word by word basis. This information is reported to the host PC via the dual port RAM on the ATT-DAS PC/16.

In Activity mode, an eight bit count is kept for each RT/TR/SA combination. These counts are incremented each time the corresponding RT/TR/SA is addressed on the bus. By reading the Activity counts, it is possible to determine which RT/TR/SA‘s are being addressed on the bus, and also the rate at which they are being addressed. Activity is concurrent with Acquisition and Monitoring.

In Acquisition mode, the Bus Monitor filters and time tags received messages to 1uS accuracy. Received Messages can be filtered by RT, TR bit, and SA. Acquired data which fulfils the acquisition filter conditions is placed into an 8K FIFO for subsequent reading by the host PC. An interrupt can be generated when the FIFO becomes half full. Acquisition is concurrent with Monitoring and Activity.1

In Monitor mode, the Bus Monitor filters and time tags received messages to 1uS accuracy. Monitor can monitor data in real time. Received Messages can be filtered by RT, TR bit, and SA. Monitored data which fulfils the monitor filter conditions is placed into one of 255 monitor buffers in the dual port RAM buffer for subsequent reading by the host PC. An interrupt can be generated when any RT/TR/SA combination is addressed on the bus. Monitoring is concurrent with Acquisition and Activity.

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