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From: ForthNet@willett.UUCP (ForthNet articles from GEnie)
Newsgroups: comp.lang.forth
Subject: Category 6,  Topic 15
Message-ID: <157.UUL1.3#5129@willett.UUCP>
Date: 5 Jan 90 10:47:04 GMT
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Category 6,  Topic 15
Message 118       Sun Dec 24, 1989
F.SERGEANT [Frank]           at 15:11 CST

    Dan & Bob -  re complex carry in RTX -

    P. 18 of RTX 2001A data sheet, under "step divide" says "The contents of
TOP and NEXT are then jointly shifted left one bit (32-bit left shift), where
the value shifted into the last significant bit of NEXT is the value of the
Borrow bit on the first pass, or the value of the Complex Carry bit on each of
the subsequent passes.

   P. 89 of the RTX Programmer's Reference Manual shows a diagram of an extra
single-bit adder whose carry-in is the regular carry-out of the ALU and whose
carry-out is the Complex Carry.  Just which two bits are added by this extra
adder seem to depend on various factors including the particular instruction
being executed.

   Apparently the complex carry is only of interest during the step math
instructions (& possibly only on divide?).  The following pages of the Prog.
Ref. Manual give more information but that's all I feel up to digging out.

  -- Frank
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