SAF-C164SM Infineon Technologies, SAF-C164SM Datasheet - Page 75

• Manufacturer Part Number: SAF-C164SM
• Description: 16-Bit CMOS Microcontroller
• Manufacturer: Infineon Technologies

Because logical ALU operations cannot produce an invalid result, the V-flag is cleared
by these operations.
The V-flag is also used as a ‘Sticky Bit’ for rotate right and shift right operations. With
only using the C-flag, a rounding error caused by a shift right operation can be estimated
up to a quantity of one half of the LSB of the result. In conjunction with the V-flag, the
C-flag allows evaluation of the rounding error with a finer resolution (see
For Boolean bit operations with only one operand, the V-flag is always cleared. For
Boolean bit operations with two operands, the V-flag represents the logical ORing of the
two specified bits.
Table 4-2
C-Flag
0
0
1
1
Z-Flag: The Z-flag is normally set to ‘1’ if the result of an ALU operation equals zero,
otherwise it is cleared.
For the addition and subtraction with carry, the Z-flag is only set to ‘1’, if the Z-flag already
contains a ‘1’ and the result of the current ALU operation additionally equals zero. This
mechanism is provided to support multiple precision calculations.
For Boolean bit operations with only one operand, the Z-flag represents the logical
negation of the previous state of the specified bit. For Boolean bit operations with two
operands, the Z-flag represents the logical NORing of the two specified bits. For the
prioritized ALU operation, the Z-flag indicates whether the second operand was zero.
E-Flag: The E-flag can be altered by instructions which perform ALU or data movement
operations. The E-flag is cleared by those instructions which cannot be reasonably used
for table search operations. In all other cases, the E-flag is set depending on the value
of the source operand to signify whether the end of a search table is reached or not. If
the value of the source operand of an instruction equals the lowest negative number
which is representable by the data format of the corresponding instruction (‘8000
the word data type, or ‘80
cleared.
MULIP-Flag: The MULIP-flag will be set to ‘1’ by hardware upon entrance into an
interrupt service routine when a multiply or divide ALU operation was interrupted before
completion. Depending on the state of the MULIP bit, the hardware decides whether or
not a multiplication or division must be continued after the end of an interrupt service.
The MULIP bit is overwritten with the contents of the stacked MULIP-flag when the
return-from-interrupt-instruction (RETI) is executed. This normally means that the
MULIP-flag is cleared again afterwards.
User’s Manual
Shift Right Rounding Error Evaluation
V-Flag
0
1
0
1
H
’ for the byte data type), the E-flag is set to ‘1’; otherwise, it is
Rounding Error Quantity
-
0 <
4-18
No rounding error
Rounding error
Rounding error
Rounding error
Central Processing Unit (CPU)
C164CM/C164SM
Table
Derivatives
V1.0, 2002-02
-
<
=
>
1
1
1
/
/
/
4-2).
2
2
2
LSB
LSB
LSB
H
’ for