I am almost there - 2 sawtooth oscillators set 7 semitones apart and a flanger on the output.
Sounds pretty close but I cannot get the portamento to "glide" between the transitions.
The aim is to sound like the start of this...
 
https://www.youtube.com/watch?v=SzBJQnD7TRM 
 
I have recorded a load of 16th notes (E, C#, A etc). I have also tried a single note with a repeater but the results are the same.
 
I can only get the glide when the notes overlap (legato) in which case there is no attack on the new note so it doesn't sound right. 
Otherwise the note transitions seem to happen immediately without that nice portamento effect.
 
Can anyone help?
 
Thanks,
ZT

Well I solved this myself - when I used an older synth plugin (Timewarp 2600) the Portamento effect worked as predicted and glided between 16th note transitions.
 
I still think that the same effect should be possible on newer synth plugins, just don't know how.

Different synths (or manufacturers) implement portamento/glide differently.

They always have.

Some require legato playing to glide and if a key is released before the next one is played they don't glide. Others apply the glide setting to every note.

Some only retrigger the envelopes when notes are played cleanly with no overlap, others retrigger the envelopes for every key press.

Some offer options for how portamento/glide is handled.