I having trouble sending data out under interrupts from a buffer. The buffer was declared in xdata and i have a counter that is used to index into it. So when an interrupt occurs, the data is loaded into my SPI tx buffer, ie SPIBUF = txbuffer[index]; index++; All i seem to get is all zero's but if i use the index to send data i get something. ie SPIBUF = index; David
The external memory is inside an ASIC. I actually found something interesting. txbuffer[0] = 0xaa; txbuffer[1] = 0x11; txbuffer[2] = 0x22; // Try transmitting data; // NB 1 - txbuffer[0] = 0xaa; P1 = txbuffer[0]; // P1 has 7 segment displays connected to it. If i don't include NB 1 just before writing it to P1 then it displays 0x00 but if i put NB 1 in and hence initial location 0 again it displays the correct value. Is this something funny with the compiler or the ASIC? David
So you're saying this works (ie, 0xAA appears on the 7 segment displays):
txbuffer[0] = 0xaa; txbuffer[1] = 0x11; txbuffer[2] = 0x22; txbuffer[0] = 0xaa; P1 = txbuffer[0];
txbuffer[0] = 0xaa; txbuffer[1] = 0x11; txbuffer[2] = 0x22; P1 = txbuffer[0];
Better yet, what's the assembler code generated for the "example" code you posted? Jon
One guess is that txbuffer points to "nowhere". What is being read from the external data bus is only the charge left from a previous access. Try
txbuffer[0] = 0xaa; txbuffer[1] = 0x11; P1 = txbuffer[0];
Yes that is correct. My buffer is: xdata unsigned char txbuffer[BUFFSIZE] This is from the list file. ; SOURCE LINE # 548 0044 900000 R MOV DPTR,#txbuffer 0047 74AA MOV A,#0AAH 0049 F0 MOVX @DPTR,A ; SOURCE LINE # 549 004A A3 INC DPTR 004B 7411 MOV A,#011H 004D F0 MOVX @DPTR,A ; SOURCE LINE # 550 004E A3 INC DPTR 004F 7422 MOV A,#022H 0051 F0 MOVX @DPTR,A ; SOURCE LINE # 551 0052 A3 INC DPTR 0053 7433 MOV A,#033H 0055 F0 MOVX @DPTR,A ; SOURCE LINE # 552 0056 A3 INC DPTR 0057 7444 MOV A,#044H 0059 F0 MOVX @DPTR,A ; SOURCE LINE # 553 005A 900000 R MOV DPTR,#txbuffer 005D E0 MOVX A,@DPTR 005E F590 MOV P1,A ; SOURCE LINE # 567 548 1 txbuffer[0] = 0xaa; 549 1 txbuffer[1] = 0x11; 550 1 txbuffer[2] = 0x22; C51 COMPILER V6.14 551 1 txbuffer[3] = 0x33; 552 1 txbuffer[4] = 0x44; 553 1 P1 = txbuffer[0]; The symbols in dscope when looking at the disassembly window make little sense, looks like other variables have been moved, something strange with dscope. For example: 552: txbuffer[4] = 0x44; c:0x1938 A3 INC DPTR; c:0x1939 7444 MOV A,#QueueSize(0x44) c:0x193b F0 MOVX @DPTR,A 553: P1 = txbuffer[0]; Not sure about that one. This is from the memory map: txbuffer . . . . . . . . . . . . . . . PUBLIC XDATA ARRAY 0065H 50 I guess it depends on whether DPTR has been loaded with the correct address for txbuffer. David
From that assembly listing, everything looks exactly correct. My guess is that your memory doesn't work correctly (or as you expect). 552: txbuffer[4] = 0x44; c:0x1938 A3 INC DPTR; c:0x1939 7444 MOV A,#QueueSize(0x44) c:0x193b F0 MOVX @DPTR,A 553: P1 = txbuffer[0]; This is all exactly correct. The debugger disassembles your code. The disassembly EXACTLY matches the listing that you provided. Which, I might add, is exactly what it should be. This kinda reminds me of a project I looked at were the programmer duplicated every move into R0. For example,
mov a, #12h mov r0, a mov r0, a mov a, @r0
Thanks for the info. The disassembly looked funny because of the MOV A, #QueueSize which is another variable declared somewhere else. The listing made sense, the QueueSize in the disassembly though confused me. David