Infineon Technologies C166S V2, User Manual

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User Manual
C166S V2
Central Processing Unit
User Manual 2-88 V 1.7, 2001-01
numbers. If the MSV-flag indicates an arithmetic overflow, the MAC result of an
operation is not valid. The MSV-flag is a ’Sticky Bit’. Once set, other MAC operations
cannot affect the status of the MSV-flag. Only a direct write operation can clear the
MSV-flag.
• ME-Flag: The ME-flag is set if the accumulator extension MAE contains significant
bits. The ME-flag is set if the nine highest accumulator bits are not all equal.
• MSL-Flag: The MSL-flag is set if an automatic saturation of the accumulator has
happened. The automatic saturation is enabled if the MS-bit of the MAC Control Word
register MCW is set. The MSL-Flag can be also set by instructions which limit the
contents of the accumulator. If the accumulator has been limited, the MSL-Flag is set.
The MSL-Flag is a 'Sticky Bit'. Once set, it cannot be affected by the other MAC
operations. Only a direct write operation can clear the MSL-flag.
• MV-Flag: The addition, subtraction, and accumulation operations set the MV-flag to 1
if the result exceeds the maximum range of signed numbers (80’00000000
H
to
7F’FFFFFFFF
H
); otherwise, the MV-flag is cleared. Note that if the MV-flag indicates
an arithmetic overflow, the result of the integer addition, integer subtraction, or
accumulation is not valid.
2.7.11 The MAC Unit Control Word MCW
This bit addressable register controls the operation of the MAC Unit. It can be accessed
via any instruction capable of addressing an SFR.
MCW
MAC Control Word
SFRb Reset Value: 0000
H
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
0 0 0 0 0 MP MS 0 0 0 0 0 0 0 0 0
r r r r r rw rw r r r r r r r r r
Field Bits Type Description
MP [10] rw One-bit scaler control
0 Multiplier product shift disabled
1 Multiplier product shift enabled
MS [9] rw Saturation control
0 Saturation disabled
1 Saturation enabled