INTRODUCTION The 73A-455 Module is a printed circuit board assembly for use in a card cage conforming to the VXIbus Specification, such as the 73A-021 used in the CDS 73A IAC System. It allows the system controller in an ATE system to communicate with and test devices that conform to the MIL-STD-1553A/B data bus now being used in many military aircraft and communications systems. The 73A-455 Module consists of two identical VXIbus instruments in a singleslot VXIbus C-size package. Each of the two separate and independent channels, labeled A and B, has its own VXIbus logical address, its own interrupt, and a complete set of controls and indicators. NOTE: Each channel of the 73A-455 is truly an independent instrument. Therefore, not only must each separate channel be completely programmed, but all switches on each channel must be properly set. Failure to do so could affect the proper operation of the 73A-455. In addition, the user should pay close attention to proper wiring if any of the 73A-455’s auxiliary inputs and outputs are used. Since each channel must be individually programmed, the descriptions in this manual should be taken to apply to either channel of the module. For example, one of the channels could be set to the 1553 Bus Controller Simulator mode of operation, and the other to 1553 Bus Monitor mode operation. The 73A-455 Module offers three modes of operation for each channel: ► 1553 Bus Controller (BC) Simulator ► 1553 single or multiple Remote Terminal (RT) Simulator ► 1553 Bus Monitor In the Bus Controller Simulator mode, each channel of the 73A-455 has the ability to communicate with any or all of the 32 remote terminals (31 real devices plus broadcast mode) specified by MIL-STD-1553A/B. Each channel is loaded by the system controller with a bus controller message sequence list and data lists for each RT to be addressed. When instructed to do so by the system controller, the selected 73A-455 channel transmits pre-programmed messages to the respective RT(s). Any response data received from the RT is stored in on-card memory for that channel. In the RT Simulator mode, each channel of the 73A-455 Module can simultaneously emulate any or all of the different RTs. The system controller preloads the 73A-455 with the appropriate response data and status words for each simulated RT. Data received from the 1553 bus by the 73A-455 is stored in on-card memory for that channel for later evaluation. In the Bus Monitor mode, the selected channel of the 73A-455 Module assumes an essentially passive role; it simply observes and stores all bus traffic. Up to 30,000 data, command, or status words can be stored in channel memory for later evaluation. The 73A-455 allows introducing controlled errors into the transmitted data stream for each channel to provide worst-case testing of 1553 bus devices. These errors include incorrect parity, erroneous 1553 Manchester encoding, zero crossing errors of ±150 ns, dropped data bits, interword data gaps, incorrect or invalid 1553 sync patterns, incorrect RT response times, incorrect number of data bits per word, incorrect number of words per message, invalid signal levels, and common-mode signal injection. On received data, the 73A-455 Module can distinguish between incorrect transition time errors, Manchester errors, dropped data-bit errors, bit count errors, parity errors, incorrect sync errors, terminal response time errors, interword data-gap errors, word count errors, and message format errors such as incorrect RT address, missing RT response, invalid status words, invalid mode code usage, and invalid broadcast mode usage. The 73A-455 Module self test capability is programmable with a single command. Each channel is tested independently. Each channel of the module is programmed by sending ASCII characters to the 73A System from the system controller. Data is also returned to the system controller as ASCII characters. Depending on the context, the two components of the 73A-455 may be referred to in this manual as VXIbus instruments, module channels A and B, or 1553 channels. Note that certain terms used in this manual have very specific meanings in the context of a VXIbus System. A list of these terms is presented in the VXIbus Glossary (Appendix C).