Class 2: Conditional Br<Elnch Instructions; Class 3: Shift Instructions; Class 4: Copy Instructions - Xerox 530 Language And Operations Reference Manual

CLASS 2: CONDITIONAL BRANCH INSTRUCTIONS
Conditional Branch instructions perform a branch if a test
for
a
given condition is "true".
If
the condition being
tested is not true, the instruction acts as a "no operation ",
and control passes to the next instruction in sequence. The
form forConditional Branch instructiol"s is
OP
, I±:
~i:~:~~:~.e~:t.,l
Class 2 instructions are written in symbolic form according
to the following syntax:
label m a
1.
The mnemonic operation code (m) determines the value
of OP (bits 0-6).
2.
The argument address (a) must be within self-relative
addressing range (-256 to +255). These instructions
may not specify indexing or indirect addressing.
The instruction is incompletely translated and tagged as an
error if the symbolic address is outside the self-relative ad-
dressing range.
The instructions in Class 2 are:
Mnemonic
BAN
BAZ
BEN
BNO
BNC
BIX
BXNO
BXNC
Function
Branch if Accumulator Negative
Branch if Accumulator Zero
Branch if Extended Accumulator Negative
Branch if No Overflow
Branch if No Carry
Branch on Incrementi ng Index
Branch on Incrementing Index and No
Overflow
Branch on Incrementing Index and No Carry
CLASS 3: SHIFT INSTRUCTIONS
The Shift instruction is capable of performing eight different
kinds of shift on an operand stored in the accumulator or ex-
tended accumulator. The amount of shift is determined by
the 5-bit shift count,
wh:~h
may be any number in the range
o
through 31. The kinds of shift available are:
Single register shift of accumulator only (general
register 7)
Double register shift of extended accumulator and accu-
mu lator together (general registers 6 and
7).
These reg-
isters are treated as a 32-bit accumulator with register6
to the left of register
7.
Arithmetic shift Circulur shift
Right shift Left sh i ft
The form for the Shift instruction is
OP
,) 1 2 ji4
16 Conditional Branch/Shift/Copy Instrucl ions
Class 3 instructions are written in symbol ic form according
to the following syntax:
label rn
5.'
x, b
1.
The mnemonic operation code (m) determines the va lue
of OP (bits 0-10).
2.
The argumenf (c, x, b) defines the shift count.
The instructions in Class
3
are:
Mnernonic
SCLS
SCLD
SCRS
SCRD
SALS
SALD
SARS
SARD
Function
Shift Circldar Left Single
Shift Circular Left Double
Shift Circular Right Single
Shi ft Circular Right Double
Shift Arithmetic Left Single
Shift Arithmetic Left Double
Shift Arithmetic Right Single
Shi
ft Arithmetic Right Double
Index and base tags are permitted in these instructions; how-
ever, such use can change the direction and type of shift
by increasing the shift count beyond the maximum value (31).
Bits for values in excess of 31 overflow into bit positions
8-10, which control the type of shift performed.
If
the
count exceeds 31, the assembler generates an error notation.
CLASS 4: COpy INSTRUCTIONS
The Copy instructions are used to perform a variety of logi-
cal and arithmetic operations between any two general reg-
rsters. One register, called the source register, contains
one of the operands; the other register, called the destination
register, contains the second operand (if one
is
required)
and is the register into which the result is loaded.
The general registers are identified as follows:
~egister
Function
0 Zero
Program address
2 Li nk address
3
T empora ry storage
4
Index 1
5
Index
2
(base address)
6 Extended accumulator
7
Accumulator
When execution of a Copy instruction begins, the
P
register
contains the address of the instruction following the Copy.
The form for the Copy instructions
is
OP