mpfj
Joined: 09 Sep 2003
Posts: 95
Location: UK
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| Bug in table read with large tables ... |
 Posted: Mon Feb 02, 2004 8:46 am |
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I'm sure people have come across this before, but it still appears to be present in version 3.184 (with a PIC18F8720)
In the code below, I'm printing some text using two different methods ... one looks up each character and calls the "putch" routine, the other calls a "print string" routine.
The first version works fine, the second fails horribly ... because ...
... just before the line that reads "CALL 1000", the register 0xFF7 (TBLPTRH) is initialised by the first method, but *not* by the second !! 
| Code: |
.................... // display item text
.................... for (j = 0; (c = setup_item_text[i][j]) != 0x00; j++) {
6C8C: MOVLB A
6C8E: CLRF xFC
6C90: MOVLB B
6C92: CLRF x8C
6C94: MOVLB 0
6C96: MOVFF AFB,B8B
6C9A: MOVLB B
6C9C: CLRF x8E
6C9E: MOVLW 19
6CA0: MOVWF x8D
6CA2: MOVLB 0
6CA4: CALL 1C5A
6CA8: MOVFF 02,B01
6CAC: MOVFF 01,B00
6CB0: MOVLB A
6CB2: MOVF xFC,W
6CB4: MOVLB B
6CB6: ADDWF 01,W
6CB8: MOVWF 01
6CBA: MOVLW 00
6CBC: ADDWFC 02,W
6CBE: MOVWF 03
6CC0: MOVF 01,W
6CC2: MOVLB 0
6CC4: MOVFF FF2,B02
6CC8: BCF FF2.7
6CCA: MOVFF 03,FF7
6CCE: CALL 1000 <----- this calls the table read function
6CD2: MOVLB B
6CD4: BTFSC x02.7
6CD6: BSF FF2.7
6CD8: MOVWF 01
6CDA: MOVLB 0
6CDC: MOVFF 01,AFD
6CE0: MOVLB A
6CE2: MOVF xFD,F
6CE4: BTFSC FD8.2
6CE6: GOTO 6CFC
.................... display_putch(c);
6CEA: MOVLB 0
6CEC: MOVFF AFD,B77
6CF0: CALL 22FE
.................... }
6CF4: MOVLB A
6CF6: INCF xFC,F
6CF8: GOTO 6C90
....................
.................... display_put_string(setup_item_text[i]);
6CFC: MOVLB B
6CFE: CLRF x8C
6D00: MOVLB 0
6D02: MOVFF AFB,B8B
6D06: MOVLB B
6D08: CLRF x8E
6D0A: MOVLW 19
6D0C: MOVWF x8D
6D0E: MOVLB 0
6D10: CALL 1C5A
6D14: MOVFF 02,03
6D18: MOVF 01,W
6D1A: MOVLB B
6D1C: MOVWF x00
6D1E: MOVLB 0
6D20: MOVFF B00,B01
6D24: MOVLB B
6D26: MOVF x01,W
6D28: MOVLB 0
6D2A: CALL 1000 <----- this calls the table read function
6D2E: IORLW 00
6D30: BTFSC FD8.2
6D32: GOTO 6D48
6D36: MOVLB B
6D38: INCF x01,F
6D3A: CLRF x19
6D3C: MOVWF x18
6D3E: MOVLB 0
6D40: CALL 5DB8
6D44: GOTO 6D24
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In fact, I've just experminented with some code and found the breaking point. I haven't tested these, but consider the two pieces of code below ...
First, set the second array dimension to 0x80 and ... tada ... a "CLRF FF7" instruction is created.
| Code: |
const char setup_test_text[2][0x080] = {
"12345678901234567890",
"12345678901234567890"
};
0FF0: MOVFF FF2,0E
0FF4: BCF FF2.7
0FF6: CLRF FF7
0FF8: ADDLW 0E
0FFA: MOVWF FF6
0FFC: MOVLW 10
0FFE: ADDWFC FF7,F
1000: MOVLW 00
1002: MOVWF FF8
1004: TBLRD*+
1006: MOVF FF5,W
1008: BTFSC 0E.7
100A: BSF FF2.7
100C: RETURN 0
.................... display_put_string(setup_test_text[i]);
6E2A: MOVLB B
6E2C: CLRF x8C
6E2E: MOVLB 0
6E30: MOVFF AFB,B8B
6E34: MOVLB B
6E36: CLRF x8E
6E38: MOVLW 80
6E3A: MOVWF x8D
6E3C: MOVLB 0
6E3E: CALL 1D34
6E42: MOVFF 02,03
6E46: MOVF 01,W
6E48: MOVLB B
6E4A: MOVWF x00
6E4C: MOVLB 0
6E4E: MOVFF B00,B01
6E52: MOVLB B
6E54: MOVF x01,W
6E56: MOVLB 0
6E58: CALL 0FF0
6E5C: IORLW 00
6E5E: BTFSC FD8.2
6E60: GOTO 6E76
6E64: MOVLB B
6E66: INCF x01,F
6E68: CLRF x19
6E6A: MOVWF x18
6E6C: MOVLB 0
6E6E: CALL 5E9A
6E72: GOTO 6E52
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Now if we change the dimension to 0x81 ... whoops ... the FF7 register does not get set up !!
| Code: |
const char setup_test_text[2][0x081] = {
"12345678901234567890",
"12345678901234567890"
};
0FF0: MOVFF FF2,0E
0FF4: BCF FF2.7
0FF6: ADDLW 0C
0FF8: MOVWF FF6
0FFA: MOVLW 10
0FFC: ADDWFC FF7,F
0FFE: MOVLW 00
1000: MOVWF FF8
1002: TBLRD*+
1004: MOVF FF5,W
1006: BTFSC 0E.7
1008: BSF FF2.7
100A: RETURN 0
.................... display_put_string(setup_test_text[i]);
6E2A: MOVLB B
6E2C: CLRF x8C
6E2E: MOVLB 0
6E30: MOVFF AFB,B8B
6E34: MOVLB B
6E36: CLRF x8E
6E38: MOVLW 81
6E3A: MOVWF x8D
6E3C: MOVLB 0
6E3E: CALL 1D34
6E42: MOVFF 02,03
6E46: MOVF 01,W
6E48: MOVLB B
6E4A: MOVWF x00
6E4C: MOVLB 0
6E4E: MOVFF B00,B01
6E52: MOVLB B
6E54: MOVF x01,W
6E56: MOVLB 0
6E58: CALL 0FF0
6E5C: IORLW 00
6E5E: BTFSC FD8.2
6E60: GOTO 6E76
6E64: MOVLB B
6E66: INCF x01,F
6E68: CLRF x19
6E6A: MOVWF x18
6E6C: MOVLB 0
6E6E: CALL 5E9A
6E72: GOTO 6E52
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Am I doing something wrong, or have CCS still not got table lookup sorted out properly ?
Regards
Mark |
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