Hi I want to use the second data pointer available in Dallas, since i am reading my port and then immediatly writing this data to external ram.All this has to be done in ISR in 10us. I am using in line assembly but the code is not working when i use both data pointers. void external0(void) interrupt 0 using 1 { //TRACK1[LEN_TRK1++]=XBYTE[0x8000]; //TRACK1[LEN_TRK1++] = XBYTE[0x8001]; //The above two C statements are replaced by the below mentioned Assembly code #pragma ASM SETB DPS ; DPS=1 ACTIVE DPTR1 MOV DPTR,#08000H MOVX A,@DPTR ; READ INC DPTR CLR DPS ; DPS=0 ACTIVE DPTR0 MOV DPL,LEN_TRK1+01H MOV DPH,LEN_TRK1 MOVX @DPTR,A ; WRITE INC DPTR SETB DPS ; DPS=1 ACTIVE DPTR1 MOVX A,@DPTR ; READ CLR DPS ; DPS=0 ACTIVE DPTR0 MOVX @DPTR,A ; WRITE INC DPTR MOV LEN_TRK1+01H,DPL MOV LEN_TRK1,DPH #pragma ENDASM } Thanx Faisal
Looking at your assembly code you are using the statements clr dps & setb dps but the dps register is a byte not a bit. As far as I recall the DPS register is not bit addressable so you cannot set and clear the SEL bit within it directly. Dallas recommended using the inc dps instruction to flip back and forth between the dptrs. Of course you have to start by initialising it to a known value.
I am not using Reg520.h but reg51.h, and i have defined DPS as sbit. sbit DPS=0x86;