| 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 DSCR RA,RB | 6F | RA | RB | |(RB)| <= 32
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Description. The concatenated contents of registers RA and RA+1 are shifted cyclically N positions, where register RB contains the count, N. If the count is positive ((RB0)=0), the shift direction is left.
If the count is negative (2's complement notation, (RB0)=1), the shift direction is right. The condition status, CS, is set based on the result in RA and RA+1.
Note: N = 0 represents a shift of zero positions.
Note: If |N| >= 32, the fixed point overflow occurs, no shifting occurs, and this instruction is treated as a NOP (see Section 5.96).
Note: (See "Description" of the double shift cyclic instruction, DSLC (see Section 5.17), for the definition of shift operations.)
Note: The contents of RB remain unchanged, unless RA = RB; in this event, the contents are shifted N positions.
Register Transfer Description.
PI4 <-- 1, exit, if |N| >= 32;
(RA,RA+1) <-- (RA,RA+1) Shifted left cyclically by (RB) positions
if 32 >= (RB) >== 0;
(RA,RA+1) <-- (RA,RA+1) Shifted right cyclically by -(RB) positions
if 0 >= (RB) >== -32;
(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, RB, CS, PI