Table of Contents
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SYSTEM
MICROCODEI~
This section contains a description of the computer system's mic-
rocode and
an introduction
on how to read the system's
Look Up
Table
(LUT)
and
Microprogram
Listings.
During
the
hardware
training course, detailed instructions on how to read the LUT and
Microprogram Listings will be presented as well
as
instructions
on
how
to use the microcode in conjunction with the Maintenance
Panel as a troubleshooting aid. (Complete
LUT
and
Microprogram
List ing s are
conta ined in the HP 3000 Se r ies I I I Comp ute r Sys tem
Microprogram Listing Manual, part
no. 30000-90136
and
are
not
repeated in this manual.)
&-1.
GENERAL INFORMATION
The microcode causes the CPU's hardware to execute the
functions
required
to
perform
the
operations
specified
by the machine
instruction set.
Therefore, in order
to
fully
understand
the
microcode
definitions
contained
in
this
section, it is first
necessary to be completely familiar with the stack
and
pipeline
operations
discussed
in Section II.
Specifically, review para-
graphs 2-16 through 2-28 and 2-71 through 2-128.
5-2.
Stack Element Locations
The stack has a topmost element (TOS) which is logically quantity
A.
Similarly, the stack has logical quantities B, C,
and D that
correspond
to
the
second
(TOS-l),
third
(TOS-2), and fourth
(TOS-3) words of the stack, respectively.
The logical quantities
A,
B,
C, and D can be
either in the CPU TOS registers or in mem-
ory as
determined by the Stack Register
(SR Register).
If the
SR Register's contents equal zero, none of the logical quantities
(A, B, C, or D) are in the TOS registers, but are located in some
memory locations SM, SM-l, SM-2, and SM-3, respectively.
At all
times however, there are four TOS registers (RA, RB, RC,
and
RD
Registers)
that
are
named by the renamer logic as discussed Fin
paragraph 2-96.
In the microprogram field codes, RA, RB, RC, and
RD
refer to the hardware RA,
RB,
RC, and
RD
Registers and not
to
the
logical
quantities A, B, C, and D.
There is a relationship
however.
For any of the logical quantities (A, B, C, and D), the
state of the SR Register indicates where the quantity is as list-
ed in table 5-1.
For example; if the SR Register contents
equal
zero
(table 5-1), then the logical quantity B is in memory loca-
tion SM and,
if the field code
RB
is used,
the
content
of
the
register
named
RB
is
affected and not the logical quantity
B.
That is, for this case, the
RB,
RC, and
RD
Registers can be
used
as
scratch
pads
without affecting the logical quantities B,
C,
and D.
Manipulation of the TOS registers is discussed further in
paragraph 5-3 through 5-6.
5-1
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