The 73A-455 MIL-STD-1553A/B bus simulator 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 used in many military aircraft and communications systems.
The 73A-455 module consists of two identical VXIbus instruments in a single-slot 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. Each channel must be individually programmed and all switches on each channel must be properly set.
The 73A-455 has three modes of operation for each channel:
- 1553 Bus Controller Simulator mode: Each channel of the 73A-455 can communicate with any or all of the 32 remote terminals specified by the MIL-STD-1553A/B. Each channel is loaded by the system controller with a bus controller message sequence list and data lists for each Remote Terminal to be addressed. Any response data received from the Remote Terminal is stored in on-card memory for that channel
- 1533 single or multiple Remote Terminal Simulator mode: Each channel can simultaneously emulate any or all of the different Remote Terminals. The system controller preloads the 73A-455 with the appropriate response data and status words for each simulated Remote Terminal. Data received from the bus by the 73A-455 is stored in on-card memory for that channel for later evaluation
- 1553 Bus Monitor mode: The selected channel of the 73A-455 assumes a 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
Controlled errors can be introduced into the transmitted data stream for each channel to provide worst-case testing of 1553 devices. There 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 Remote Terminal 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 can distinguish between incorrect transition time 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 Remote Terminal address, missing Remote Terminal response, invalid status words, invalid mode code usage, and invalid broadcast mode usage.
The 73A-455 self test capability is programmable with a single command (each channel 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.
- Configuration: MIL-STD-1553 Bus Controller Simulator, single or multiple Remote Terminal Simulator, or Bus Monitor
- 1553 bus coupling
- Direct coupling: 1:1 turns ratio, 55 Ω isolation resistor each leg
- Transformer stub coupling: 1:0.707 turns ratio
- Buffer capability: 30,000 22-bit words - 16 bits data, 6 bits error/sync code. Can be allocated between 32 transmit buffers, 32 receive buffers, and a single Bus Controller Sequence List or Remote Terminal Response Time List. Allocation is user-controlled
- 1553 analog output: Level-programmable to ~250 different levels
- Analog output voltage range
- 35 Ω, direct-coupled output: 0.20 to 8.20 Vp-p
- 70 Ω, direct-coupled output: 0.30 to 13.75 Vp-p
- 1000 Ω, direct-coupled output: 0.75 to 34.4 Vp-p
- 70 Ω, transformer-coupled output: 0.60 to 24.2 Vp-p
- Analog output noise content: 50 mVp-p
- Analog output current drive
- 260 mArms maximum, direct-coupled output
- 380 mArms maximum, transformer-coupled output
- Analog output short-circuit protection
- The direct-coupled output can be shorted for several minutes without degradation of the transmitter
- The transformer-coupled output should not be shorted. Shorting can cause damage to the module
- 1553 analog input: Programmable to ~250 different levels
- Analog input (maximum): 40 Vp-p differential
- Transition time error detection: Time from one threshold crossing to the next threshold crossing is nominally expected to be 0.5, 1.0, 1.5, or 2.0 µs, per MIL-STD-1553. The receiver checks that this time is reliably within 62.5 ns of the nominally expected time
- Time base: 16 MHz crystal oscillator
- VSIbus compatibility: Fully compatible with the VXIbus specification for message-based instruments with the Halt switch in the ON position
- VXI device type: VXI message based instrument, VXIbus revision 1.2
- VXI protocol: Word serial
- VXI card size: C size, one slot wide