Xerox 560 Reference Manual

Designation Function
CC Condition code. This generalized 4-bit
code indicates the nature of the results of an
instruction. The significance of the condition
code bits depends upon the particular instruc-
tion just executed. After an instruction is
executed, the BRANCH ON CONDITIONS
SET (BCS) and BRANCH ON CONDITIONS
RESET (BCR) instructions can be used singly
or in combination to test for a particular con-
dition code setting. (These instructions are
described in Chapter 3, "Execute/Branch
Instructions") •
FR
FS
FZ
FN
In some operations onlya portion of the con-
dition code is involved; thus, the term CC 1
refers
to the first bit of the condition code,
CC2 to the second bit, and CC3 and CC4,
respectively, to the third and fourth bits. Any
program
can change the current value of the
condition code by executing either the LOAD
CONDITIONS AND FLOATING CONTROL
IMMEDIATE (LCFI) or the LOAD CONDI-
TIONS AND FLOATING CONTROL (LCF)
instruction. Any program can store the cur-
rent condition code by executing the STORE
CONDITIONS AND FLOATING CONTROL
(STCF) instruction. These instructions are
described in Chapter 3, ;;Load/~tore
Instructions" .
Floating round mode control (see FN below).
Floating significance mode control (see FN
below).
Floating zero mode control (see FN below).
Floating normalize mode control. The four
floating-point mode control bits (FR, FS, FZ,
and FN) control the operation of the basic
processor with respect to invoking the round-
off mode of floating-point calculations,
checking floating-point significance, gen-
erating zero results, and normalizing the
results of floating-point additions and sub-
tractions, respectively. (The floating-point
mode controls are described in Chapter 3,
"Floating-Point Instructions".) Any program
can change the state of the current floating-
point mode controls by executing either the
LCFI or the LCF instruction. Any program can
store the current state of the current floating-
point mode controls by executing the STCF
instruction.
Designation Function
MS Master/slave mode control. The basic pro-
cessor is in the master mode when this bit and
the mode altered bit (bit 61) both contain
zero; it is in the slave mode when this bit
contains one. (See MS for a description of
master-protected mode.) A master mode or
master-protected mode program can change
this mode control bit by executing the
LOAD PROGRAM STATUS WORDS (LPSD),
EXCHANGE PROGRAM STATUS WORDS
(XPSD),
PUSH STATUS (PSS), or PULL STATUS
(PLS) instruction. These privi leged instruc-
tions are described in Chapter 3, "Control
Instructions" •
MM Memory map control. The memory map is in
effect when this bit position contains a one.
A master mode or master-protected mode pro-
gram can change the· memory map control by
executing an LPSD, XPSD, PSS, or PLS
instruction.
DM Decimal mask. The decimal arithmetic trap
(see "Trap System", later in this chapter) is
permitted to occur when this bit position con-
tains a one. The conditions that cause a
decimal arithmetic trap are described in Chap-
ter 3, II Decimal Instructions". The decimal
trap mask can be changed by a master mode
or
master-protected mode program executing
the LPSD, XPSD, PSS, or PLS instruction.
AM Arithmetic mask. The fixed-point arithmetic
overflow trap is permitted to occur when this
bit contains one. The instructions that can
cause fixed-point overflow are described in
the section "Trap System", later in this chap-
ter. The arithmetic trap mask can be changed
by a master mode or master-protected mode
program
executing an LPSD, XPSD, PSS, or
PLS instruction.
IA
WK
CI
II
Instruction
address. This 17-bit field contains
the virtual address of the next instruction to
be executed.
Write key. This field contains the 4-bit key
used in
conjunction with a write lock in the
memory
write protection feature. A master
mode or
master-protected mode program can
change the value of the write key by execu-
ting an LPSD, XPSD, PSS, or PLS instruction.
Counter interrupt group inhibit (see EI, below).
Input/output interrupt group inhibit (see EI,
below).
Main Memory 29

Xerox 560 Specifications

General

Brand	Xerox
Model	560
Category	Printer
Language	English