53A-412 Tektronix Programmable Digital I/O Card

The Aeroflex / Tektronix / CDS 53A-412 Programmable Digital I/O Card is a printed circuit board assembly for use in a Aeroflex / Tektronix / CDS 53/63 Series System. The 53A-412 provides 48 TTL and CMOS compatible, bidirectional digital I/O lines. For programming convenience, and to help in defining proper test flow, these 48 programmable I/O signal lines are organized as six 8-bit bytes. Two available options further extend the usefullness of the Card by adding optical isolation or open collector capability to the I/O.

Each of the six bytes can be completely and independently configured under full program control. All commands and responses are normally in ASCII hex notation for ease of programming, and to insure compatibility with the widest range of systems controllers. However, a binary capability is also supplied standard for those applications requiring increased data transfer speed.

Data output can be controlled as bits, as individual bytes, and/or as groups of bytes. Control of the output be directly applied on a command basis, or further qualified and controlled by using external handshakes, or by means of a programmable time count.

Data input is also fully under program control. The card can report the state of all input bytes, groups of input and/or output bytes, and single bits of a byte. Input data can be updated on a command request basis, or on a qualified basis using external handshakes.

User-defined masks can be overlaid on the data prior to output. Masks may also be applied to individual input bytes before they are returned to the system controller to improve data post-processing speed and to promote ease of data interpretation.

The sense of inputs and outputs can be set to either active high or active low under program control. The active edge can also be programmed for handshake lines. All I/O lines are both TTL and CMOS compatible, with up to 24 mA of sink current provided for each output. With option 01 installed, the I/O section of the card is fully isolated from system ground using optoisolators and an isolated power supply contained on the card.

External (handshake) control signals are provided for output and input data control. Output data control signals are Ready For Data (RFD), Data Available (DAV), and External Tri-State control (ETSO - ETS5). Input data control signals are Data Ready (DRD) and Data Acknowledge (DAK).

A binary I/O mode is provided which allows a total of 6000 bytes to be allocated for buffered binary I/O through the card. Two modes are provided for binary input: Mode 1 inputs data as long as there is free memory in the buffer to accept it, while Mode 2 overwrites the oldest data in memory when the input buffer is filled. Binary input is controlled by the Data Ready handshake. Data can be simultaneously read from the input buffer while new data is being strobed in, dynamically freeing memory for additional input. The card can also be programmed to generate an interrupt when the input buffer is full.

Binary output can be controlled by either the Ready For Data handshake or on a programmable time basis from 100 µs to 858 seconds. Two modes are provided: mode 1 outputs data as long as there is data in the output buffer. Mode 2 allows pre-loading the output buffer, then defining a 'thread' sequence to control how preloaded data is output. For mode 1, data can simultaneously be loaded into the card while data is being output. The number of bytes left to be output can be read at any time, and the card programmed to generate an interrupt when the output buffer is empty. For mode 2, an interrupt can be programmed to occur when a breakpoint occurs in the sequence.

The 53A-412 provides full access to system status information, which is especially helpful during system t: ruble-shooting, software de-bugging, and operational system checks. At any time, the system controller can read the state of the external handshake lines, the programmed I/O configuration, the programmed active edges of all handshake signals, which handshake signals are active, the programmed logic sense of each I/O byte, the tri-state condition of each output byte, and up-to-date error data.

Built-in-Test-Equipment (BITE) is provided on the card by an internal loop-back path that allows the card to be tested with its outputs tri-stated, verifying I/O paths for each byte. A self test is automatically performed on power up, or it can also be commanded. Front panel LEDs indicate the error status, data handshake signals, current tri-state conditions, input/output configuration, and individual I/O bits. In addition, the Query and Operation commands can be used to determine the current state of the card during operation.