ST20-C1 Datasheet, PDF (127/205 Pages) STMicroelectronics – Instruction Set Reference Manual

8 Instruction Set Reference
mac
multiply accumulate
Code: 21 F2
Description: Multiply Areg and Breg, and add in Creg. The most significant word of
the result is placed in Breg and the least significant in Areg. This can be used in
forming the double length product of Areg and Breg, with Creg as carry in, treating
the Areg and Breg values as signed but Creg as unsigned.
Definition:
Areg′
Breg′
← low_word (accum64)
← high_word (accum64)
Creg′
← Areg
where
accum64 = (Breg × Areg) + Creg_unsigned
– the value of accum64 is calculated as a 64-bit value
Status Register:
No effect
Comments:
Secondary instruction.
See also: ldiv mul umac
Chapter 5.
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