Asm sleep - pbp sleep

[richard]

if you are going to do this sort of thing in asm then you need to understand how banked memory access is
used for this chip. hint [ baudcon is not in access bank ]

[MOUNTAIN747]

if you are going to do this sort of thing in asm then you need to understand how banked memory access is
used for this chip. hint [ baudcon is not in access bank ]

Thanks guys for all your replies. I really do appreciate the time you've
taken.
So Richard, I should have understood what you were saying the first time. I converted all code to PBP and it looks like RCIDL is set after all. However it didn't change the results.
I then went to battery power, no change. Still a reset every 2.14sec. I also changed several of the configs with no change in results. I may mark this one up as part of the magical mystery tour as I have a work around for the problem. This is one of a couple problems that I could never solve. The other was the inability to make RA.7 a digital I/O. I wonder if my software has some corruption. Yea, when all else fails blame it on the software. Wayne

[Ioannis]

Did you set WDT to OFF?

Ioannis

[Ioannis]

OK, here is the explanation about the NOP:

When the SLEEP instruction is being executed, the next
instruction (PC + 1) is prefetched. For the device to
wake-up through an interrupt event, the corresponding
interrupt enable bit must be set (enabled). Wake-up
occurs regardless of the state of the GIE bit. If the GIE
bit is clear (disabled), the device continues execution at
the instruction after the SLEEP instruction. If the GIE bit
is set (enabled), the device executes the instruction
after the SLEEP instruction, then branches to the interrupt
address (0004h). In cases where the execution of
the instruction following SLEEP is not desirable, the
user should have a NOP after the SLEEP instruction.
The WDT is cleared when the device wakes up from
Sleep, regardless of the source of wake-up.

The key is that before SLEEP the next command is prefetched and might not be what one wants right after a wake, especially after wake from interrupt.

Ioannis

[richard]

a 2 sec reset looks very likely to be wdt



after disabling wdt i would try something like this

SleepMode:
    PortA.1=0     ;Indicator LED out on entering SLEEP
ASM
    BANKSEL BAUDCON  ;bank 3
    BTFSS   BAUDCON,RCIDL  ;Check for High, no receive in progress
    GOTO $-1                
    BSF BAUDCON,WUE        ;Wake on Rx from Master 
    BANKSEL 0  ;bank 0
    BSF  PORTC,1   ;LED 
    BCF INTCON ,7
    SLEEP
    nop
    BSF INTCON ,7
ENDASM
    PortA.1=1                   ;Indicator LED ON  at exit SLEEP
    return
    end

[sayzer]

.....

  SLEEP
    nop
    BSF INTCON ,7

Wayne,
Pay attention to Rihard's code there. The first ting after SLEEP must be NOP.
You did not have NOP as the first thing atfer SLEEP in your code.

and WDT is OFF in config; how can it be an issue?

[MOUNTAIN747]

Success at last, well kind of. New questions are raised as the problem is solved.
Alain's code dimnstrates the purpose of the sleep state, low power, all ports off. This is not required but is good practice.

I followed richards ASM modifications of my poor attempt (years since I wrote ASM. I was trying to brush up)

WDT was always off in Configs so it was never WDT event. Will later read Config addresses to confirm I got what I wanted in memory.

As I enter the ASM code blockk, no LED can be executed after the test for RCIDL and before SLEEP.
Place BSF Portx.x before RCIDL test and SLEEP works.
Place BSF Portx.x after RCIDL test and SLEEP dies not works.
Place BSF Portx.x after BSF BAUDCON, WUE and SLEEP dies not works.
Place BSF Portx.x after BSF INTCON.7 t and SLEEP dies not works.

Before entering the ASM block i can turn on as many LED's as I like and Sleep works as it should.

OK so this is a strange behavure that does not fit any RESET format I can find in the data sheet.

Regarding the data sheet section memtioned by Ioannis.
Wake up will occure regardless of state of GIE bit.
PC SLEEP +1 is prefeched durring SLEEP.

SLEEP with GIE set: NOP may be needed in this case!
Test RCIDL
Set WUE
SLEEP
Wake and exicute next instruction
Call ISR
return to Sleep +2
continue program

SLEEP with GIE clear: no NOP needed but it can't hurt!
Test RCIDL
Set WUE
SLEEP
Wake and exicute next instruction
No ISR called
continue program

In my case I will WAKE on EUSART single byte %00000000. I need the ISR to read RCREG and clear RCIF, then discard Break character. Single NOP will be needed.

So now the adventure of the WAKEUP routine. Thank you for alll your help.
Wayne

[Ioannis]

Glad you did it! Similar cases we faced I guess too.

But that makes me wonder, if we try so hard to solve such things on a PIC, what would happen on a more complex MCU? Would then take years to find what is wrong???

Ioannis