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Read-Only Author
David Pleydell Posted
26-Jun-2001 02:59 GMT Toolset
C51 |  array inside interrupt function David Pleydell 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
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Read-Only Author
Jon Young Posted
26-Jun-2001 04:43 GMT Toolset
C51 | RE: array inside interrupt function Jon Young 1) Check if your external memory is working. Try:
..
txbuffer[0] = 0xAB;
..
SPIBUF = txbuffer[0];
index++;
2) Check if your indexing is correct.
Verify "SPIBUF = index;" generates "0,1,2,...", not just something.
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Read-Only Author
David Pleydell Posted
26-Jun-2001 05:12 GMT Toolset
C51 | RE: array inside interrupt function David Pleydell 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
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Read-Only Author
Andrew Neil Posted
26-Jun-2001 09:09 GMT Toolset
C51 | RE: array inside interrupt function Andrew Neil 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];
But this doesn't work (0 appears on the 7 segment displays):
txbuffer[0] = 0xaa;
txbuffer[1] = 0x11;
txbuffer[2] = 0x22;
P1 = txbuffer[0];
Sounds like something funny with your ASIC's memory addressing?
What is the full 'C' definition of txbuffer?
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Read-Only Author
Jon Ward Posted
26-Jun-2001 14:00 GMT Toolset
C51 | RE: array inside interrupt function Jon Ward Better yet, what's the assembler code generated for the "example" code you posted?
Jon
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Read-Only Author
David Pleydell Posted
27-Jun-2001 00:32 GMT Toolset
C51 | RE: array inside interrupt function David Pleydell 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
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Read-Only Author
Jon Ward Posted
27-Jun-2001 01:09 GMT Toolset
C51 | RE: array inside interrupt function Jon Ward 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
When asked why the double move into r0, he responded, "Because the first one didn't take."
My question was, "If the first mov r0 didn't take, how do you know that the second one always would?"
Jon
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Read-Only Author
David Pleydell Posted
27-Jun-2001 01:22 GMT Toolset
C51 | RE: array inside interrupt function David Pleydell 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
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Read-Only Author
Jon Young Posted
26-Jun-2001 23:22 GMT Toolset
C51 | RE: array inside interrupt function Jon Young 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];
If you get an answer of 0x11, check the address of txbuffer. |
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