AFAIR without going and looking it up (lazy!) the CD4094 has the extra flip-flop and also a latch so data on outputs does not change while shifting. I use 2 in series as outputs in one design and 2 x CD4021 as equivalent inputs. Russell McMahon ge----- From: Ian Chapman >On Tuesday 20th October 1998, John Payson wrote: >>I think the '595 is a much nicer part for many applications. Its eight >>outputs won't change until you hit a "latch enable" signal (which you >>may do after shifting in your data). The one feature the '595 lacks >>which would be nice to have would be a QH' output which was delayed by >>1/2 clock (to allow the devices to be cascaded without race conditions) >..... >John's comment gave me a scare when I realised that one of my designs >uses two directly cascaded '595s. This seems to be a drop-off in the >design of this part as the Philips data sheet for the HC/HCT595 states >that the Q7' (QH') output is intended for cascading - and yet it is >clear from closer examination that a skew of 10ns or more between the >shift clocks of the respective devices could result in marginal timing >and possibly incorrect operation. As John says, an extra flip-flop >acting on the falling edge of the shift clock would solve this.