Toshiba – Toshiba TMP87CP24AF User Manual
Page 35
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TOSHIBA
TMP87CM24A/P24A
However,
an
acceptance
of
external
interrupt
0
cannot
be
disabled
by
the
EF;
therefore,
if
disablement
is
necessary,
either
the
external
interrupt
function
must
be
disabled
with
INTOEN
in
the
external
interrupt
control
register
(INTOEN)
or
interrupt
processing
must
be
avoided
by
the
program.
(When
INTOEN
=
0,
the interrupt latch IL3 isnotset, therefore, the falling edge of the INTO pin input cannot be detected.)
Example 1 : Disables an external interrupt 0 using INTOEN:
LD
(EINTCR), OOOOOOOOB ; INT0EN<-0
Example 2 : Disables the processing of external interrupt 0 under the software control (using bit 0
at address OOFO
h
as the interrupt processing disable switch):
PINTO:
TEST
(OOFOH). 0
JRS
T, SINTO
RETI
SINTO:
: Interrupt processing :
RETI
Returns without interrupt processing if(OOFOH)o= 1
VINTO :
DW
PINTO
(2)
General-Purpose register save/restore processing
During
interrupt
acceptance
processing,
the
program
counter
and
the
program
status
word
are
automatically
saved
on
the
stack,
but
not
the
accumulator
and
other
registers.
These
registers
are
saved
by
the
program
if
necessary.
Also,
when
nesting
multiple
interrupt
services,
it
is
necessary
to
avoid using the same data memory area for saving registers.
The following method is used to save/restore the general-purpose registers:
© General-purpose register save/restore by register bankchangeove:
General-purpose
registers
can
be
saved
at
high-speed
by
switching
to
a
register
bank
that
is
not in use. Normally, bank 0 is used for the main task and banks 1 to 15 are assigned to
interrupt
service
tasks.
To
increase
the
efficiency
of
data
memory
utilization,
the
same
bank
is assigned for interrupt sources which are not nested.
The
switched
bank
is
automatically
restored
by
executing
an
interrupt
return
instruction
[RETI] or [RETN]. Therefore, it is not necessary for a program to save the RBS.
Example: Register Bank Changeover
PINTxx :
LD
RBS, n
interrupt processing
RETI
; Switches to bank n
(1//S
at
8
M Hz)
; Restores bank and Returns
Figure 1-25. Saving/Restoring General-purpose Registers
3
-
24-35
2002
-
10-03