Analog Devices ADSP-BF53x Blackfin, Reference

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Multiply Accumulators (Multipliers)
2-38 ADSP-BF53x/BF56x Blackfin Processor Programming Reference
• If an overflow or underflow has occurred, the saturate operation
sets the specified Result register to the maximum positive or nega-
tive value. For more information, see the following section.
Saturating Multiplier Results on Overflow
The following bits in
ASTAT
indicate multiplier overflow status:
• Bit 16 (
AV0
) and bit 18 (
AV1
) record overflow condition (whether
the result has overflowed 32 bits) for the
A0
and
A1
accumulators,
respectively.
If the bit is cleared (=0), no overflow or underflow has occurred. If
the bit is set (=1), an overflow or underflow has occurred. The
AV0S
and
AV1S
bits are sticky bits.
• Bit 24 (
V
) and bit 25 (
VS
) are set if overflow occurs in extracting the
accumulator result to a register.
Multiplier Instruction Summary
Table 2-10 lists the multiplier instructions. For more information about
assembly language syntax and the effect of multiplier instructions on the
status flags, see
Chapter 15, “Arithmetic Operations.”
In Table 2-10 , note the meaning of these symbols:
• Dreg denotes any Data Register File register.
• Dreg_lo_hi denotes any 16-bit register half in any Data Register
File register.
• Dreg_lo denotes the lower 16 bits of any Data Register File
register.
• Dreg_hi denotes the upper 16 bits of any Data Register File
register.