Byte-String Instructions - Xerox 560 Reference Manual

ExamEle 2, L = 6:
Before execution
After execution
EDO X'000938F7 X'000938F7
E655B483 E655B483
02F1 BO' 02F1BO'
(DECA) xxxxxxxx X'ooOOOooO
xxxxxxxx 00000000
xxxxxxxx 00000987
xxxxxxxx 6543210D'
CC
xxxx 0001
UNPK
UNPACK DECIMAL DIGITS
(Byte index alignment, continue after interrupt)
If no illegal digit or sign is detected in the decimal accu-
mulator (assumed to be in packed decimal format), UNPACK
DECIMAL DIGITS converts the contents of the low-order
L bytes of the decimal accumulator to zoned decimal format
and stores the result, as a byte string, from the effective
byte location to the effective byte location plus 2L-2.
The contents of the four low-order bit positions of the deci-
mal accumulator are used to select the sign code for the
last digit of the string; for all other digits, the zones are
1111 (X'F'). The contents of the decimal accumulator re-
main unchanged, and only 2L-l bytes of memory are altered.
If the decimal accumulator contains more significant infor-
mation than is actually unpacked and stored, CC2 is set to
1;
otherwise, CC2 is reset to O. If the result in memory is
zero, the resulting sign remains unchanged.
Affected: (EBltoEBL+2L-2), Trap: Decimal arithmetic
CC1, CC2
zoned (DECA) - EBL to EBL + 2L -2
Condition code settings:
2 3 4 Result of UNPK
o
Illegal digit or sign detected, instruction
aborted
o
0 - - All significant infor-
mation zoned and
stored
o
Some signifi cant
information not
zoned and stored
86 Byte-String Instructions
No illegal digit
or sign detected,
instruction
completed
Example 1, L
=
10:
Before execution
(DECA) X'ooOOOOOO
00000001
23456789
0123456D'
EDO xxxxxxxx
xxxxxxxx
xxxxxxxx
xxxxxxxx
xxxxxx
CC xxxx
Example 2, L
=
8:
(DECA)
EDO
Before execution
X'OOOOOOOO
23000000
10001234
0012345C'
xxxxxxxx
xxxxxxxx
xxxxxxxx
xxxxxx
CC xxxx
Example 3, L
=
4:
(DECA)
EDO
CC
Before execution
X '0000 100 1
00001002
00001003
0001004F'
xxxxxxxx
xxxxxxxx
xxxx
After execution
X'OOOOOOOO
00000001
23456789
0123456D'
X'FOFOFOFl
F2F3F4F5
F6F7F8F9
FOF1F2F3
F4F5D6'
OOxx
After execution
X '00000000
23000000
10001234
OO12345C'
X'F1FOFOFO
F1F2F3F4
FOFOF1 F2
F3F4C5'
01xx
After execution
X'OOOOlool
00001002
00001003
0001004F'
X'FOFOFOF1
FOFOC4'
Olxx
BYTE -STRING INSTRUCTIONS
Five instructions provide for the manipulation of strings of
consecutive bytes. The byte-string instructions and their
mnemonic codes ore as
f()lI()ws~
Instruction Name Mnemonic
Move Byte String MBS
Compare Byte String
CBS