Circuitry for Transforming 'STROBE' Edges into 'STROBE' Pulses

Circuitry for Transforming 'STROBE' Edges into 'STROBE' Pulses

                  ----       ---------               ----
Data Bit 0           |       |       |               |
                     ---------       -----------------

                  ----                       ---------
Data Bit 1           |                       |       |
                     -------------------------       ----

                  ----   -----   -----   -----   -----
-Strobe              |   |   |   |   |   |   |   |   |
                     -----   -----   -----   -----   -

                  ----       ---------       ---------
Edge Mode Strobe     |       |       |       |       |
                     ---------       ---------       ----

              Figure 1 - Possible Input Strobe Signals

      Disclosed is circuitry to allow a sequential memory measurement
instrument to convert 'STROBE' edges into 'STROBE' pulses of the
proper phase.  This circuitry will also double the frequency of the
input signal.

      A sequential memory system is built to accept data from a
remote hardware system.  The remote hardware system must send n bits
of data to be stored and a 'STROBE' signal that signifies when the n
bits of data are valid.  Fig. 1 shows what two of the possible n data
bits could look like.  The '-Strobe' signal in Fig. 1 is an example
of the proper negative going 'STROBE' signal.  This '-Strobe' signal
must have a negative going edge every time the data bits can change
to a new value.  The interface could not provide the '-Strobe'
signal.  The signal that could be provided was the signal called
'Edge Mode Strobe' in Fig. 1.  This signal changes edges everytime
the data is valid.  The problem is to provide circuitry that will
transform the 'Edge Mode Strobe' into the same form as the '-Strobe'
signal.  This requires that each edge of the 'Edge Mode Strobe' be
converted into a negative going pulse.  It is also desired that the
circuit also accept the '-Strobe' signal and work correctly.

                                          ---------
                                          |       |
Edge Mode Strobe -------------------------> XOR   | -Strobe
                   |  ...