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Encoding ALU functions

For ALU instructions the OTA fields encode the ALU functions as following:

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
OTA     Function       Remarks
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1       ADD            Add
2       SUB            Subtract
3       CMP            Compare
4       AND            Logical AND  
5       OR             Logical OR
6       XOR            Logical XOR
7       SHFL           Shift Left
8       SHFR           Shift Right
9       SWP            Swap Nibbles
10-15   (Reserved)

Note:

All functions employ register A as left operand. The result is latched into A except for CMP which affects flags without altering A content.