HP 3000 III Series Manual page 182

Sys tern Microcode
Table 5-1. Stack Element Locations
,--
-----.-~"-"-·-·--l-"-- ------~--.---"--.-.,
I I
Loca tions
, SR Registe r ,
'Contents
'---1----1---1-----
, , A ' B ' C 'D
,
' "
,
,---------------",
.
-',----",---',----
, 0 , SM'SM-l'SM-2'SM-3
, 1 , RA , SM ISM-llsM-2
, 2 , RA ,
RB ,
SM ISM-l
, 3
I
RA
I
RB ,
RC , SM
, 4 ,
RA ,
RB ,
RC ,
RD
, ' I "
5-3. PUSH. The microinstruction Store Field code PUSH accom-
plishes three things:
a. It stores the output of the Shifter in the RD Register.
b. It increments the SR Register.
c. It renames the TOS registers so that the register named the
RA Register becomes (: =) the
RB
Register; the registe r named
the
RB
Register: = the RC Registe r; the register named the
RC Register := the
RD
Registe r; and the register named the
RD
Register := the RA Register. Effectively, combining steps
a and c, PUSH stores the contents of the U-Bus in the TOS
location.
5-4. POP. The micr oin s tr uction Spec ial Field code POP accom-
plishes two things.
a. It decrements the SR Register.
b. It renames the TOS registers so that the register named the
RA Register:= the
RD
Register; the register named the
RB
Register
: = the
RA
Register; the register named the
RD
Reg ister : = the
RB
Register; and the register named the
RD
Register := the RC
Register. Effectively, POP removes or "pops" the top element
from the stack.
5-5. QUP. The microinstruction Store Field code QUP (Stack
Marker Pointer Up) effectively stores the contents of the U-Bus
in the stack at location SM+l. For example, if stack locations S
and S-l are in the TOS registers and locations S-2 is the first
stack element in memory {SM),QUP places the contents of the U-Bus
in a TOS register at stack location S-2 and
8M
:=
S~3.
(To main-
tain stack integrity, the SR Register must be incremented with
the Special Field code INSR to indicate the addition of the TOS
register element.) When QUP is executed, TNAME (output of the
Adder for the Mapper) := NAME (output of Namer Register) plus the
contents of the SR Register to rename the TOS registers. (Refer
to paragraph 2-96.) The register temporarily named
RA :
= U-Bus as
5-2