BNC 577 - Manual (Page 8)

Model 577 Operating Manual 4
3 Pulse Concepts and Operations
3.1 Counter Architecture Overview
Signal Source
3.2 System Timer Functions
The System Timer functions as a non-retriggerable, multi-vibrator pulse generator. This means that once started,
depending on the mode, the timer will produce pulses continuously. Before pulses can be generated, the timer
must first be armed and then receive a start pulse. Arming the counter is done by pressing the Run/Stop key.
With external trigger disabled, the Run/Stop key also generates the start command for the counter. With external
trigger enabled, the external trigger provides the start pulse. In either case, once started, the counter operation is
determined by the System Mode Generator. Standard modes include:
Continuous Once started T
0
pulses are generated continuously.
Single Shot One T
0
pulse is generated for each start command.
Burst
‘n’ T
0
pulses are generated for each start command.
Duty Cycle Once started T
0
pulses cycle on and off continuously.
The T
0
pulses are distributed to all of the start inputs of the Channel Timers and Mode Generators
3.3 Channel Timer Functions
The Channel Timer functions as a non-retriggerable, delayed, one shot pulse generator. This means that the
timer will only generate one delayed pulse for every start pulse received. Once the channel timer has started
counting, additional start pulses will be ignored until the pulse has been completed (non-retriggerable). The start
pulse for each channel is provided by the internal T
0
pulse generated by the Internal System Timer. Whether or
not a pulse is generated for each T
0
pulse is determined by the Channel Mode Generator. Standard modes
include:
Normal A pulse is generated for each T
0
pulse.
Single Shot One pulse is generated at the first T
0
pulse, after which the output is
inhibited.
Burst A pulse is generated for each T
0
pulse, 'n' times, after which the output is
inhibited.
Duty Cycle
‘n’ pulses are generated for each T
0
pulse after which the output is inhibited
for ‘m’ times. The cycle is then repeated.
Different modes may be selected for each output, allowing a wide variety of output combinations. Each output
may also be independently disabled or gated (using the external gate input).