| MIL-STD-1750A: Standard sixteen-bit computer architecture | ||
|---|---|---|
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Addr
Mode Mnemonic Format/Opcode
8 4 4
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R DNEG RA,RB | B5 | RA | RB |
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Description. The negative (i.e., the 2's complement) of the Derived Operand, DO (i.e., the contents of register RB and RB+1), is stored into register RA and RA+1 such that register RA contains the MSH of the result. The condition status, CS, is set based on the result in register RA and RA+1.
Note: The negative of zero is zero.
Note: The negative of a number with a 1 in the sign bit and all other bits zero is the same word, and causes fixed point overflow to occur.
Register Transfer Description.
(RA, RA+1) <-- -DO;
PI4 <-- 1, exit, if DO = 8000 0000
16;
(CS) <-- 0010 if (RA,RA+1) = 0;
(CS) <-- 0001 if (RA,RA+1) < 0;
(CS) <-- 0100 if (RA,RA+1) > 0;
Registers Affected. RA, RA+1, CS, PI