Browse Prior Art Database

Programmable Single-Shot With Asynchronous Clock

IP.com Disclosure Number: IPCOM000101340D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 86K

Publishing Venue

IBM

Related People

Price, SL: AUTHOR [+2]

Abstract

Disclosed is a circuit using an 8-bit counter and an RS flip/flop which are connected to a microcontroller in order to produce a programmable-length single-shot pulse (-REF PULSE). The counter may be clocked asynchronously from the microcontroller. The method used to allow asynchronous clocking is applicable to any parallel-loaded ripple counter.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Programmable Single-Shot With Asynchronous Clock

       Disclosed is a circuit using an 8-bit counter and an RS
flip/flop which are connected to a microcontroller in order to
produce a programmable-length single-shot pulse (-REF PULSE).  The
counter may be clocked asynchronously from the microcontroller.  The
method used to allow asynchronous clocking is applicable to any
parallel-loaded ripple counter.

      Refer to Fig. 1 for a schematic drawing of the circuit. The
counter input register is preloaded with a value which determines the
desired pulse length.  It is not necessary to load the counter again
unless the circuit is powered down or a new pulse length is desired.

      The microcontroller fires the single-shot by pulling CLOAD low,
then high.  Toggling CLOAD loads the counter and resets the Pulse
Flip/Flop (F/F) to a low state, enabling the counter clock (CCLKEN).
When the counter reaches hex FF, Ripple Carry Output (-RCO) is pulled
low, resetting the Pulse F/F and disabling the counter clock.  The
circuit will not be released to count until it is loaded again.  The
fact that all counter F/fs are frozen as "1"s is crucial to the
operation of this circuit.

      This particular embodiment uses an 8-bit counter with input
registers, but the basic principles may be applied to any
parallel-loaded ripple counter.  There is feedback within the circuit
to stop the counter when it reaches maximum value, and the counter
may be clocked asynchronously from the device which loads or
activates it.

      Figs. 2 and 3 help to illustrate why the counter may be clocked
asynchronously.  Fig. 2 is a gen...