53A-541 Tektronix Universal Digitizing Counter Card

The Aeroflex / Tektronix / CDS 53A-541 Universal Digitizing Counter (UDC) Card with Time Tag Memory is a printed circuit board assembly for use in the 53A/63A System; two channels are provided that can measure signals in the sub-Hertz to 10-MHz frequency range. The 53A-541 Card incorporates a universal timer/counter and a digitizing counter into a single instrument operating in two possible modes: I) The Timer/Counter mode, whose functions include the traditional measurements associated with a universal counter: frequency, event count, period, period average, pulse width, pulse width average, time interval, time interval average, duty cycle, and duty cycle average. 2) The Time Tag Memory mode, consisting of two real-time and two post-processing sub-modes, lets the user analyze an input signal on a cycle to cycle basis. This is accomplished by storing the absolute time of each successive transition of the input waveform in a 28-bit by 2048-word memory. Storing absolute transition times of waveforms lets the user analyze the time-interval relationships between two waveforms, or the frequency, period, pulse width, and duty cycle characteristics of a single waveform from cycle to cycle. The real-time sub-modes allow measurement data to be read "on the fly" without halting the storing of new data. The post-processing sub-modes allow data to be read after the measurement cycle is complete.

There are several different ways to control how long the measurement cycle (or gate duration) lasts. For frequency and event-count functions in the Timer/Counter mode or when using the Time Tag Memory mode, the measurement cycle may be controlled by 1) a specified number of A or B events, 2) by a specified amount of time from 1 microsecond to 427 seconds, 3) by direct program control, or 4) by an external gate. For the averaging functions, the measurement cycle may be specified as the number of occurrences to average. The measurement cycle itself may be triggered under program control or by an external trigger.

Programmable control of input-trigger level, slope polarity, attenuation, AC or DC coupling, and input-signal enable is provided for both channels. The input-signal enable control allows the time tag memory to be used more efficiently in single channel applications. Two different methods of trigger-level programming are provided for each channel: either a programmable level or an automatic trigger-level search. The automatic trigger-level setting may be read back. Finally, a programmable A common B capability allows the A channel signal to be input to both counter channels simultaneously.

Commands are sent to the card as ASCII character strings. Data is returned 1) as an ASCII character string containing up to nine significant digits, decimal point, and an exponent, or 2) as eight binary 8-bit bytes that may be blocked into records of variable length under program control. Input may be either driven by input requests or interrupts.

Seven SMB jacks at the front-edge of the card provide easy access for the two input channels, the A-and-B reconditioned TTL outputs (normal and inverted), and the external gate.

Four LEDs at the front edge of the card visually indicate A-and-B channel triggering, gate status, and programming errors.