topic Re: Inline Assembly Troubles (Such a Noob Problem) in 8-bit Microcontrollers

Inline Assembly Troubles (Such a Noob Problem)

mjcoury — Tue, 01 Aug 2006 20:57:05 GMT

I am having some trouble with my inline assmebly. to preface everthing, this is my routine to read memory out to the serial port

void ReadRamOut(word iMemory, int iByte) {
int i = 0;
char *memory_ptr;

memory_ptr = (char*)iMemory;

for( i=0; i
SCIStartTransmit(*(memory_ptr+i));
} // end for
} // end ReadRamOut

Here is the code to write to flash

DisableInterrupts
memory_ptr = (char*)iMemory;
for( i=0; i
ctemp = gu8SCIData[i];
asm{
LDA ctemp
STA memory_ptr
}
WriteFlash();
memory_ptr++;
} // end for loop

iMode = 0x00;
gu8SCIIndex = 0;
EnableInterrupts

I show the ReadRamOut routine because that method of pointing to a memory location has worked for me... so I assumed it would work again for the inline assembly....
Now assume iMemory = 0x1600. instead of writing ctemp to the memory location 0x1600 it writes over the 0x1600 with the contents of ctemp. I have tried a few different combinations of iMemory and memory_ptr to get this to work.. Any Ideas?

Message Edited by mjcoury on 2006-08-01 08:58 AM

Re: Inline Assembly Troubles (Such a Noob Problem)

rhinoceroshead — Tue, 01 Aug 2006 21:25:13 GMT

If you just want to transfer the contents of gu8SCIData[i] into the location pointed to by memory_ptr, then you can just do this:

*memory_ptr = gu8SCIData[i];

There is really no need to fuss with the inline assembly - but the reason it might be failing could be that you are erasing the contents of the accumulator when they are needed. Try this assembly instead:

PSHA

LDA ctemp

STA memory_ptr

PULA

What is in the WriteFlash() function? Do you know that works?

Re: Inline Assembly Troubles (Such a Noob Problem)

mjcoury — Tue, 01 Aug 2006 21:56:57 GMT

void WriteFlash(void) {
byte temp = 0x00;

if ((FSTAT & 0x10) != 0) {
FSTAT |= 0x30;
}
asm {
//LDA #$CC
//STA $1600
LDA #$20
STA FCMD
LDA #$80
STA FSTAT
NOP
NOP
NOP
NOP
WFLOOP:
LDA FSTAT
LSLA
BPL WFLOOP
}
} // end WriteFlash

Yes, I know it works.. if i use
asm{
LCD #$CC
STA $1600
}
WriteFlash()

the value of 0xCC will be written to location 0x1600

Message Edited by mjcoury on 2006-08-01 09:58 AM

Re: Inline Assembly Troubles (Such a Noob Problem)

CompilerGuru — Tue, 01 Aug 2006 23:59:50 GMT

as rhinoceroshead already pointed out, such simple assignments can be made easely in C, no need for HLI.
The HLI assembly instruction "STA memory_ptr" clearly stores the content of A into the high byte of the local variable memory_ptr. If you want to store to the place were memory_ptr points to, you have to load it into H/X, and then do a STA 0,X. Just using C is much simpler tough:
*memory_ptr= ctemp;

Daniel