Intel MCS48 User Manual page 114

INSTRUCTION SET
SEL
MBO
Select
Memory Bank
(Not
in
8021
,
8022)
1110
101
Example:
PC
bit
11
is
set to
zero on next
JMP
or
CALL
instruction.
All
references
to
program
memory
addresses
fall
within
the
range
0-2047.
(DBF)-«-
Assume program
counter contains 834 Hex.
SEL
MBO
JMP
$+20
SELECT
MEMORY
BANK
JUMP TO LOCATION
48
HEX
SEL
MB1
Select
Memory Bank
1
(Not
in
8021
,
8022)
1111
10
1
PC
bit
11
is
set to
one on
next
JMP
or
CALL
instruction.
All
references
to
program
memory
addresses
fall
within the
range 2048-4095.
(DBF)-«-
1
SEL RB0
Select Register
Bank
(Not
in
8021, 8022)
1100
10
1
PSW
bit
4
is
set to zero.
References
to
working
registers
0-7
address data
memory
locations 0-7.
This
is
the
recommended
setting for
normal
program
execution.
(BS)<*-
SEL RB1
Select Register
Bank
1
(Not
in
8021
,
8022)
110
1
10
1
PSW
bit
4
is
set to
one.
References
to
working
registers
0-7
address data
memory
locations 24-31.
This
is
the
recommended setting for interrupt service routines,
since locations 0-7 are
left
intact.
The
setting of
PSW
bit
4
in
effect at
the time
of
an
interrupt
is
restored
by the
RETR
instruction
when
the interrupt
service routine
is
completed.
(BS)
1
Example:
Assume
an
external interrupt
has occurred, control
has passed
to
program
memory
location
3,
and
PSW
bit
4
was zero before the
interrupt.
LOC3-
JNI INIT
;JUMP
TO ROUTINE
'INIT
IF
INTERRUPT INPUT
IS
ZERO
Mnemonics copyright
Intel
Corporation 1976.
4-32