794 Quad Gate/Delay Generator



The Quad Gate/Delay Generator, Model 794, complies fully with the NIM specification TID-20893 and is packaged in a single width module. In monostable mode, Gate/Delay periods may be adjusted either locally or remotely from less than 50nSec to more than 10 seconds. Each channel also operates in a Set/Reset flip-flop mode. A bright LED indicates an active gate condition. Versatile input and output structures provide compatibility with NIM, ECL, and TTL standards. Further flexibility is afforded by programming jumpers mounted on the printed circuit board. These jumpers allow selected inputs and outputs to be assigned alternate logic functions or polarities.

Time-Base Section

The model 794 time-base circuit is non-updating and exhibits essentially no deadtime. Monostable Gate/Delay periods are selected by a combination of the RANGE switch and an analog programming input. A monitor test point provides a 0 to 1 Volt output which is proportional to the Gate/Delay period. Setting the Gate/Delay period with an oscilloscope is easily accomplished by pushing the TRIGGER push-button. Depressing this switch for more than 0.5 seconds causes the time-base to retrigger at a 1 KHz rate. In the bistable mode, the Gate/Delay period is equal to the interval between the arrival of the trigger and reset functions. The DELAY output always occurs at the trailing edge of the GATE output and it's output width may be adjusted by a front panel potentiometer.

Input Section

There are three ways to trigger the Model 794: (1) TRIGGER Input; (2) OR Input; (3) TRIGGER push-button. These functions are enabled in both monostable and bistable modes.

(1), The TRIGGER input is compatible with both positive TTL levels and negative NIM logic. This input presents a high impedance to positive signals and 50 ohms to negative signals. The time-base triggers on the leading edge of the input pulse regardless of its logic type. The gate period is independent of the TRIGGER pulse width.

(2), OR is a negative NIM logic input which is configured with program jumpers. The OR input is always logically OR'ed with the time base output. Assuming a quiescent time base, the GATE output width is equal to the OR input width. A program jumper enables an alternate OR mode in which the OR input also triggers the time-base. This mode produces a GATE output equal to the width of the OR input or the preset time, whichever is greater. An additional jumper allows OR to be a high impedance or 50 ohms. Note that the high impedance OR input allows multiple channels or multiple modules to be easily daisy-chained and triggered from a single source.

(3), The TRIGGER push-button offers two operating modes for manual triggering. In the single trigger pulse mode, a single output is produced by pushing and releasing the switch in less than 0.5 seconds. In retrigger mode, by pushing and holding the switch for more than 0.5 seconds produces a continuous pulse train of 1 KHz as long as the push-button is depressed.

In the bistable (FF) position, when the channel is triggered or SET, it remains in that state until reset by the negative NIM compatible RESET input or the RESET push-button. The TRIGGER and OR inputs are inhibited from setting the channel when RESET is present. The RESET input is enabled only in the bistable mode.

INHIBIT is a negative NIM compatible input. All outputs are forced to their quiescent state whenever INHIBIT is present. GATE transitions resulting from INHIBIT do not generate DELAY outputs.

A special feature of the Model 794 is the ANALOG PROGRAMMING input. Enabled by program jumpers, each input accepts 0 to +10 Volt levels and produces a 5% to 105% adjustment of the selected range. The analog voltage is received differentially to relieve the noise and common mode offsets associated with long cable runs.

Output Section

Each channel has five (5) outputs. GATE, complemented GATE, and DELAY are negative NIM current source outputs governed by the trigger rules described above. TTL is a TTL compatible output which can be assigned to either the GATE or DELAY function. A second jumper associated with TTL provides a true or complement feature. ECL is a differential ECL output conforming to CERN Note EP 79-01 and is jumper programmed to be identical to either GATE or DELAY outputs.

Bin Gate Description

The model 794 is capable of driving the bin gate of the host bin. A switch mounted on the rear panel enables or disables the BIN GATE feature. Individual channels are selected to supply this gate signal via program jumpers. More than one channel may be selected resulting in a Bin Gate which is the logical OR of the selected channels.

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