M166 datasheet(29/127 Pages) SIEMENS

29 / 127 page

30Mar98@15:00h

Semiconductor Group

Version 1.2, 12.97

C166 Family Instruction Set

Instruction Description

•Condition Flags• This part reflects the state of the N, C, V, Z and E flags in the PSW register which

is the state after execution of the corresponding instruction, except if the PSW register itself was

specified as the destination operand of that instruction (see Note).

The resulting state of the flags is represented by symbols as follows:

’*’

The flag is set due to the following standard rules for the corresponding flag:

N = 1 :

MSB of the result is set

N = 0 :

MSB of the result is not set

C = 1 :

Carry occured during operation

C = 0 :

No Carry occured during operation

V = 1 :

Arithmetic Overflow occured during operation

V = 0 :

No Arithmetic Overflow occured during operation

Z = 1 :

Result equals zero

Z = 0 :

Result does not equal zero

E = 1 :

Source operand represents the lowest negative number

(either 8000h for word data or 80h for byte data)

E = 0 :

Source operand does not represent the lowest negative

number for the specified data type

’S’

The flag is set due to rules which deviate from the described standard.

For more details see instruction pages (below) or the ALU status flags description.

’-’

The flag is not affected by the operation.

’0’

The flag is cleared by the operation.

’NOR’

The flag contains the logical NORing of the two specified bit operands.

’AND’

The flag contains the logical ANDing of the two specified bit operands.

’OR’

The flag contains the logical ORing of the two specified bit operands.

’XOR’

The flag contains the logical XORing of the two specified bit operands.

’B’

The flag contains the original value of the specified bit operand.

’B’

The flag contains the complemented value of the specified bit operand.

Note: If the PSW register was specified as the destination operand of an instruction, the condition

flags can not be interpreted as just described, because the PSW register is modified

depending on the data format of the instruction as follows:

For word operations, the PSW register is overwritten with the word result. For byte

operations, the non-addressed byte is cleared and the addressed byte is overwritten. For bit

or bit-field operations on the PSW register, only the specified bits are modified. Supposed

that the condition flags were not selected as destination bits, they stay unchanged. This

means that they keep the state after execution of the previous instruction.

In any case, if the PSW was the destination operand of an instruction, the PSW flags do NOT

represent the condition flags of this instruction as usual.

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