HP29C - DSZ ISZ Question

[Mike T.]

I have never owned an HP29C (nor given the prices on e-bay am I ever likely to own one either) but would like to know if the operation of the DSZ/ISZ instructions on the HP29C/HP19C is similar to the DSE/ISG functions on the HP11C - obviously in the case of the HP29C/HP19C the test is against a zero value, but did the HP29C use the fractional and integer parts of the I register in the same was as the HP11C (and HP34C) or was it was it altogether simpler?

Thanks.

Mike T.

[Andrés C. Rodríguez (Argentina)]

I don't have a 29/19 either, but have used a 29C for a short while many years ago. If I recall correctly (I apologize in advance if I'm wrong), as the test value was zero and as the step was always one, the fractional part is always zero´. For comparison, in the HP41 any register used for ISG/DSE operations has the format: iiiii.fffcc where i is the initial or current value, fff the final value and cc the step.

[Bram]

Small addition: the fractional part doesn't need to be zero. It's just being ignored.

[Mike T.]

To summarize - the fractional part of the value in R0 is ignored (and left unchanged?) while integer part is incremented/decremented and next instruction is skipped if the result is zero. Please correct me if I'm wrong!

Many thanks for the feedback.

Mike T.

[Bram]

fractional part is indeed left unchanged and of course the test is done on the integer part only.

[Mike T.]

Thank you...