HP 3000 III Series Manual page 187

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System Microcode
Table 5-2. R-Bus Field Code Definitions (Continued)
1 - - - 1
1
I
Field
1 I
La bel and Name
1
Code
I
Des cr ip t ion
I
----~--
I .I
~-~~--~----~----------
:
RB 1010 The RB R-Bus field code is used to
1
read the second TOS register (loca-I
tion S-l). SR must be greater than
1.* During execution, TNAME be-
comes NAME and the R-Bus Register
is loaded as follows:
If TNAME
=
00 then R-BUS :
=
TRIR
If TNAME
=
01 then R-BUS
:=
TR2R
If TNAME
=
10 then R-BUS :
=
TR3R
If TNAME
=
11 then R-BUS
:=
TROR
R-BUS
RC
RD
0101
1001
1000
The RBUS R-Bus field code causes
R-Bus Reg iste r to rema in unchanged.
The RC R-Bus field code is used to
read the third TOS registe r (loca-
tion S-2).
SR
must be greater than
2.* During execution, TNAME be-
comes NAME and the R-Bus Register
is loaded as follows:
If TNAME
=
00 then R-BUS :
=
TR2R
If TNAME
=
01 then R-BUS
:=
"rR3R
If TNAME
=
10 then R-BUS
:=
TROR
If TNAME
=
11 then R-BUS :
=
TRIR
The RD R-Bus field code is used to
read the fourth TOS register (loca-
tion S-3).
SR
must be equal to 4.*
During execution, TNAME becomes
NAME and the R-Bus Register is
loaded as follows:
I f TNAME
=
00 the n R-BUS:
=
T R3R
If TNAME
=
01 then R-BUS :
=
TROR
If TNAME
=
10 then R-BUS :
=
TRIR
If TNAME
=
11 then T-BUS
:=
TR2R
1---'---------------- ------- -,-.---,----------------,----.--------.----"
I*True only if RA:RD are being used as part of the stack. RA:RD
1
often are used by the microprogram as scratch pad registers
1
when not used otherwise.
I
5-7