HP 3000 III Series Manual page 155

Machine Instructions and Stack cperati6ns
4. MOVE, MVB, MVBW, CMPB, SCU,- SCW. These six instructions are
members of the move group and as such deal with strings of words
or bytes. The first three physically move a word or byte string
from one block of locations in primary memory to another. The
CMPB instruction does not move data but compares data in two
complete str ings, byte by byte. The last two also do not move-
data but scan a data str ing tpsting the str ing byte by byte
against a test character and a terminal character.
SOURCES. The MOVE, MVB, and CMPB instructions may take source
data from either the code segment or the data segment. (For ref-
erence purposes, "source" and "target" te rrn inology is retained
for CMPB, even through there is no move operation.) If bit 11 of
the instruction is a "0", source addresses are PB+ relative;
i.e., from the code segment. If bit 11 is a "1",. source addresses
are DB+ relative; i.e., from the data segment. Figure 4-9 illus-
trates both cases. Note that the target for either case is in
the DB+ area. (Disregard move-direction arrows for CMPB.) Both
source and target (MVBW) addresses are DB relative for MVBW, SCU,
and
scw.
The target need not- be "higher" than the source; figure
4-9 shows examples only.
1
1
DATA
SEGMENT
(-Countl
t
•
(+Countl
(-Countl
•
,
(+Countl
Target
Source
.:1
Count
DB
DL
(+1 (-I
Incr Decr
C
Incr Decr
B
Decr
Incr
A
Z
~
PB Relative Source
-
....
DB Relative Source
,
....
~
r
Target
CODE
SEGMENT
PB
(-Countl
1
+
,
(+Countl
P
INCREASING
ADDRESSES
PL
t::::========1
Figure 4-9. Move Examples
4-25