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System Microcode
Table 5-4.
Function Field Code Definitions (Continued)
1----~---~------l------T----~----'---~-~'--'-'-------'-'------'1
1
I
Field
I
I
I
Label and Name
1
Code
I
Descr iption
I
I
I
I
I
-'---'-~----~'-'--'--
-_._-------.;
--,_.~--_
..
_,-~----~----._
..
_--~---..-._.,_._._
..
, _._- -
_._
•.
_-
REPC (Cont)
REPN
(Repea t
N
Times)
ROM
RaMI
(ROM Inclusive)
10101
10011
10010
loads ROR2 and executes the micro-
instruction to be repeated. As long
as the Repeat FF remains set, the
content of RORI and ROR2 does not
change and is executed each cycle.
When the Skip field condition is
met, the Repeat FF is cleared, the
pipeline is filled correctly, and
the next microinstruction is fetch-
ed in the usual manner.
The REPN Function field code oper-
ates in the same manner as the REPC
code previously described.
The
difference is that REPN loads a Re-
peat Counter Registe r wi th the con-
tents of the microinstruction Skip
field.
Bits 1 thru 5 of the count-
er become ROR2 bits 5 thru 9; bit 0
of the counter becomes a 1.
The
counter content is then the two's
complement of the number of repeats
to be performed.
To utilize the
counter, the repeated microinstruc-
t ion conta ins a Special fie Id code
INCTR (Increment (bunter) and a
Skip field condition CTRM (Cbunter
Maximum) .
The Function field code ROM loads
the R-Bus Register with a l6-bit
constant obtained from the microin-
struction.
The ROM code is decoded
from RORl, loading the the R-£us
Reg iste r with bits 16 thr u 31 of
RORI.
The T-Busthen becomes the
R-Bus Register content plus the S-
Bus Register content.
The R-Bus,
Shift, Special, and Skip Field De-
coders are disabled by the ROM
code.
The Function field code RaMI loads
the R-Bus Register with a 16-bit
constant obtained from the microin-
struction.
The RaMI code is decod-
ed from RORl, loading the R-Bus
5-21
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