hello,

I am in need of some guidance please.
I am using a 17c44  with 4Mhz crystal and writing extenally to M48z02-70(16
Kbit Zeropower SRAM for ST) .
I am trying to read and write a 16 bit munber. In Mplab simulation it seems
to run fine BUT in my circuit the chip seems to write only 8 bits and reads
16bits, from looking at the data on a logic analyser. I can write 0xaa to
the lower 8 bits but do nto seem to be able to get 0x55 written into the
upper 8 bits. I do read all 16 bits.

Am I missing something simple or maing a silly mistake? Please help as I am
going around in circles

Thank you

Sharon


The bones of the code is below:

//temp data memory locations
static unsigned char high_mem1   @ 0x22;
static unsigned char low_mem1     @ 0x23;

//temp storage for read data
static unsigned char hr_mem1      @ 0x32;
static unsigned char lr_mem1      @ 0x33;

lr_mem1=0x00;   //clearing memory locations
hr_mem1=0x00;

high_mem1=0xaa;
low_mem1=0x55;

void main ()
{

//initialisation here
 for(;;)
    {
     CLRWDT();

  for(i=0;i<32000;i++)  // routine writing to SRAM from
    {
      CLRWDT();
      GLINTD=1;
      Write1();
      GLINTD=0;
    }

     for(i=0;i<32000;i++)
     {
       CLRWDT();
       Read1();
     }
   }
}

void Write1(void)
{
#asm
      CLRWDT                    ; clear the watch dog timer
        movlw    128                    ; load the table pointer with 0x8000 in SRAM
        movwf    _TBLPTRH               ;
        clrf     _TBLPTRL               ;
        tlwt     1, _high_mem1    ; high byte @ table latch    // does not seem to
write this
        tablwt 0,1, _low_mem1   ; low byte @table latch         // writes 0xaa here
#endasm
}


void Read1(void) // transfer of 8 bytes of data from program(external)
memory
                      // to data memory starting at 0x30
{
CLRWDT();               // clearing watchdog timer
#asm

        movlw    128            ; load the table pointer with 0x8000
        movwf   _TBLPTRH        ;
        clrf    _TBLPTRL        ;
        tablrd  0,1, _lr_mem1   ; get 16 bit value in table latch
        tlrd    0, _lr_mem1      ; low byte @table latch, latch @prob.mem   // reads
0xaa                                                                                                        successfully
        tablrd  1, 1,_hr_mem1   ; high byte @ table latch       // reads a random
value.. 1's
#endasm
}

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