Moto FFP Details?
6 messages in this thread
I still haven't found any paper docs on the bit-level details of the Motorola
fast-floating-point FFP numeric format.
I need to write some portable C code that maps as best as possible between IEEE
and FFP. (Yes, I know there will be some truncation involved because they're
not the same.) My usual sources of info have turned up flat…
I would think Moto would send you something. Why won't they?
—
Dale L. Larson, Intangible Assets Manufacturing
The ROM Kernel Manual – Libraries and Devices states the format of the
Motorola FFP format.
The current edition says that the format is 24 bits of mantissa in the
range [0.5, 1) followed by 8 bits of excess-64 exponent. This cannot be
correct.
The previous edition (for WB 1.3) states that it is 24 bits of mantissa in
the range [0.5, 1), then 1 sign bit and 7 bits of excess-64 exponent.
This latter seems to be the (more) correct specification.
The value is always normalised, except for 0.0 which is all zero bits.
The old RKM says that the range of values is 5.42101070e-20 to
9.22337717e18, -9.22337717e18 to -2.71050535e-20, and 0.0
I hope this makes sense.
Regards,
Shraddhan (via AP from Hertfordshire, England)
I guess I shouldn'tve overlooked the original source. 🙂
> I guess I shouldn'tve overlooked the original source.
I didn't know the RKM was the original source. I thought that the FFP
format already existed and Commodore merely used it. Or am I mistaken?
Regards,
Shraddhan (via AP from Hertfordshire, England)