[sdcc-devel] [ sdcc-Bugs-960614 ] Interrupt carry bit problem

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Bugs item #960614, was opened at 2004-05-26 09:22
Message generated for change (Settings changed) made by maartenbrock
You can respond by visiting: 
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Category: msc51(8051) target
Group: fixed
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: tony_pemberton (tonypemberton)
Assigned to: Nobody/Anonymous (nobody)
Summary: Interrupt carry bit problem

Initial Comment:
I am a newbie to SDCC, so perhaps I am missing 
something. Please also see PS below.

I seem to be having difficulties with Timer Interrupts in 
SDCC running on my Silabs C8051F310. It seems 

that optimisation stops the PSW being pushed/popped 
onto the stack. As a result, an integer operation 

causes the carry bit to change state and the program 
runs wild until a Flash violation causes a reset.

The C code for Timer2_ISR is as below.

//-----------------------------------------------------
------------------------
// 0x2b Timer2_ISR Interrupts every 15ms
//-----------------------------------------------------
------------------------
//
void Timer2_ISR (void) interrupt TF2_VECTOR critical
{
	displayButtonHoldDownTime++;
	TF2H = FALSE;		// clear Timer2 
overflow flag
	TF2L = FALSE;		// clear Timer2 
overflow flag
}

The resulting ASM code is as below.

C:/Program files/SDCC/source/TT_PROCS.C:318: void 
Timer2_ISR (void) interrupt TF2_VECTOR critical
;	-----------------------------------------
;	 function Timer2_ISR
;	-----------------------------------------
_Timer2_ISR:
	push	acc
	push	dpl
	push	dph
	setb	c
	jbc	ea,00103$
	clr	c
00103$:
	C$TT_PROCS.C$320$1$1 ==.
;C:/Program files/SDCC/source/TT_PROCS.C:320: 
displayButtonHoldDownTime++;
;     genPlus
	mov	dptr,#_displayButtonHoldDownTime
	movx	a,@dptr
	add	a,#0x01
	movx	@dptr,a
	inc	dptr
	movx	a,@dptr
	addc	a,#0x00
	movx	@dptr,a
	C$TT_PROCS.C$321$1$1 ==.
;C:/Program files/SDCC/source/TT_PROCS.C:321: TF2H 
= FALSE;		// clear Timer2 overflow flag
;     genAssign
	clr	_TF2H
	C$TT_PROCS.C$322$1$1 ==.
;C:/Program files/SDCC/source/TT_PROCS.C:322: TF2L 
= FALSE;		// clear Timer2 overflow flag
;     genAssign
	clr	_TF2L
00101$:
	mov	ea,c
	pop	dph
	pop	dpl
	pop	acc
	C$TT_PROCS.C$323$1$1 ==.
	XG$Timer2_ISR$0$0 ==.
	reti
;	eliminated unneeded push/pop psw
;	eliminated unneeded push/pop b

The version of SDCC is as below.

C:\Program Files\SDCC\bin>sdcc -v
SDCC : 
mcs51/gbz80/z80/avr/ds390/pic16/pic14/TININative/xa51
/ds400/hc08 2.4.1 (May 19 2004) (MINGW32)

I note that the serial interrupt does save the PSW, but 
others do not even if they are dummy for later 

use.

Is there a pragma or other workaround for this problem?

I guess I could code the routine in assembler but that 
rather defeats the object of using C.

Best regards,

Tony Pemberton

PS Since my original post in the forums I have been 
doing some further work. I have put the original 

message in the bug list as requested.

I found I was not using external storage declarations so 
was getting multiple references to variables. 

This was fixed, but is not really germane to the issue. I 
also tried using reg bank 1 and this fixed the 

problem - for now.

I do not use #pragma's at all in my current code.

The batch file I use is as:-

cd "C:\Program files\SDCC\bin
SDCC -c --no-xinit-opt --debug "C:\Program 
files\SDCC\source\TT_INIT.C
SDCC -c --no-xinit-opt --debug "C:\Program 
files\SDCC\source\TT_ACTION.C
SDCC -c --no-xinit-opt --debug "C:\Program 
files\SDCC\source\TT_PROCS.C
SDCC -c --no-xinit-opt --debug "C:\Program 
files\SDCC\source\TT_TABLES.C
SDCC -c --no-xinit-opt --debug "C:\Program 
files\SDCC\source\TT_MAIN.C
SDCC --debug --code-size 0x3A00 --xram-size 0x3C0 
TT_MAIN.rel TT_INIT.rel TT_ACTION.rel TT_PROCS.rel 

TT_TABLES.rel
cd "C:\Program files\SDCCGOTO END
rem Usage : sdcc [options] filename
rem Options :-
rem   -m                        Set the port to use e.g. -
mz80.
rem   -p                        Select port specific processor 
e.g. -mpic14 -p16f84
rem   ------<snip>-------
REM Options available for ease of use as comments
REM	GAMEBOY
REM	  -z   Gameboy image as file[GB]
REM	List:
REM	  -u	Update listing file(s) with link data as 
file(s)[.RST]
REM	End:
REM	  -e   or null line terminates input
:END




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