Hmm, thanks for the suggestions.

Although, even on ebay the chips are relatively expensive. The cost of the chip is more than the rest of the components in the project !

3 volt operation is no problem but I do need internal oscillator option and more I/O pins. Whereas the 877 and 877a don't offer the int osc option.

It's not really a problem of code requirements more a problem of spurious rf, even when the crystal is mounted up close to the chip. I've tried the 628 in a similar design pcb as I want to use, this with internal osc and it is rf quiet. However external xtal on an 877 does generate more rf hash locally.

Not very scientifically tested I'm sure but easily noticeable even with rf design techniques.

For what I want to achieve I suppose I might as well go to two 628's rather than a single 40 pin device for cheapness. I just thought that there was a more modern version, without a cost penalty.

The 4550 and 4620 both look attractive devices.