Tektronix 7613 User Manual

Circuit Description—7613/R7613 Service
Time-Slot Counter
Time-Slot Counter U2126 is a sequential switch which
directs the trapezoidal waveform input at pin 8 to one of its
10 output lines. These time-slot pulses are used to
interrogate the plug-in units to obtain data for the Readout
System. The Trigger pulse at pin 15 switches the Time-Slot
Counter to the next output line; the output signal is
sequenced consecutively from time-slot 1 through time-slot
10. Fig. 3-31 shows the time-relationship of the time-slot
pulses. Notice that only one of the lines carries a time-slot
pulse at any given time. When time-slot 10 is completed, a
negative-going End-of-Word pulse is produced at pin 2. The
End-of-Word pulse provides a drive pulse for the Word
Trigger stage and also provides an enabling level to the
Display-Skip Generator during time-slot 1 only.
Pin 16 is a reset input for the Time-Slot Counter. When
this pin is held LO, the Time-Slot Counter resets to
time-slot 1. The Time-Slot Counter can be reset in this
manner only when a Jump signal is received by U2155C
(see following discussion).
Word Trigger
The Word Trigger stage is made up of the 4 two-input
NOR gates contained in U2155. Quiescently, pin 2 of
U2155A is LO as established by the operating conditions of
U2155D and U2155C. Therefore, the LO End-of-Word
pulse produced by the Time-Slot Counter results in a HI
level at pin 1 of U2155A. This level is inverted by U2155B
to provide a negative-going advance pulse to the Channel
Counter.
An advance pulse is also produced by U2155A when a
Jump signal is received at pin 8 of U2155C. This condition
can occur during any time-slot (see Row Decoder for
further information on origin of the Jump signal). U2155D
and U2155C are connected as a bistable flip-flop. The
positive-going Jump signal at pin 8 of U2155C produces a
LO at pin 10. This LO is inverted by U2155D to produce a
HI at pin 13, which allows pin 9 of U2155C to be pulled HI
through R2155. The flip-flop has now been set and it
remains in this condition until reset, even though the Jump
signal at pin 8 returns to its LO level. The HI output level at
pin 13 turns on Q2159 through R2158 to pull pin 16 of the
Time-Slot Counter LO. This resets the Time-Slot Counter
to time-slot 1 and holds it there until U2155C is reset. At
the same time, a HI level is applied to pin 4 of the Timer
through CR2125 and CR2124. This HI level causes the
Timer to operate in the display-skip mode so that a
character is not generated.
The next Trigger pulse is not recognized by the
Time-Slot Counter since U2159 is locked in time-slot 1 by
U2155. However, this Trigger pulse resets the Word Trigger
3-40
"ee
7
TS-3
Ties
TS-5
~
186.
ce
~
Ts8_
TS-9
~~
T$-10
TS-1
Time-slot
pulse 1
Pin 3
ov
Time-slot
pulse 2 |
Pin 13 UW
Time-siot Ov
pulse 3 \ |
Pin 12 U
ov
Time-siot /
pulse 4
Pin 11 7
Time-slot
pulse 5 \ i
Pin 10 WT
ov
Time-siot ]
pulse 6 4
Pind ty
Time-stot : OV
pulse 7 |
Pin 7 U
Time-slot ] ov
pulse 8 :
Pin6 Wi
Time-slot ov
pulse 9 \ [
Pin 5 J
Time-siot . ov
pulse
10
|
Pin
4
uu
NOTE: Test oscilloscope externally triggered from
TP2251, Sweep rate uncalibrated.
Fig. 3-31. Time relationship of the time-slot (TS) pulses produced
by U2126.
7613

Tektronix 7613 Specifications

General

Brand	Tektronix
Model	7613
Category	Test Equipment
Language	English