HP 3000 III Series Manual page 219

System Microcode
Table 5-9. Skip Field Code Definitions (Continued)
t
--'-~----~--'----r-'--'-~--'r-~-~--'.--------~----·---·--·----I
I 1
Fie Id
1 I
1
Label and Name
1
Code
I
Des cr ipt ion
1
I I 1 I
I--·------·--·-·--I--·--·--I---------~---·~---------------I
I
NCRY (Con t)
I I
NOP2 FF if the car ry out fr om the
I
I 1 1
AL U
is ze r o.
I
I 1 I
1
NEG
01011
I
The Skip field code NEG sets the
1
I I
NOP2 FF if the U-Bus word is a neg-I
1 I
ative number (U-Bus bit
0
is a
I
I
logic
1) •
1
1 I
NEXT
11101
1
Terminates current instruction and
1
I initiates the sequence necessary to
I
begin execution of the next in-
I
struction. If stackop A has just
1
been executed and stackop B is not
I
a NOP, then the hardware executes
I
stackop B. Otherwise, the action
I
shown in the timing figure below
I
ta kes place (a,
b,
c, d, e, f ar e equal
1
length CPU clock cycles) •
1
a
b
c
d e f
Execute
1 st line
of mic-
rocode
of new
i nstr.
NOP2
P+l-)P
Select cycle
RANKl-)
RANK2
(If memory
reference,
force PADD,
BASE
to R,
S-BUS Reg's.)
NEXT
BUSL,RWP
Issue LOREQ
LUT-)
VBUS-)
ROM-)
RANKI
NIR-)CIR
NIR-)LUT
..• Mem. Sel.
cycle
DATA-)NIR
I
I
Time periods a, b, c (if present),
I
and d occur in the currently exe-
I
cuting instruction. Time periods a
I
and b must occur before d for
rnaxi~
I
mum execution speed. Otherwise, a
I
CPU freeze will occur at d. Time
I
periods a and b result from the
I
next instruction prefetch of the
1
.....
'---_._--
----~-------'_._-
--------
---_
..
_~----------~------_._._----,--,--------_.-
5-39