$� Trap Break/Reset with ON ERROR
� by Chris Davies 
� for BBC and Electron
(� (c) Acorn User April 1985
2:
<oldvec=&70
Ferrvec=&202
Posbyte=&FFF4
ZP%=&900
d[
n\ Restore error vector
x\ to Basic's � �
�LDA oldvec
�STA errvec
�LDA oldvec+1
�STA errvec+1
�\
�\ initialise ROMs
�LDA #143
�
LDX #1
�LDY #&E
�JSR osbyte
�
LDX #2
�JSR osbyte 
�
LDX #3

LDY #&FF

JSR osbyte

\

"\ create error 100 (Break) 

,BRK

6]

@$P%=�(100)+"BREAK"+�(0) 

J:

T� Point Break vector to

^#� Machine code patch - JMP &900

h*FX 247,76

r
*FX 248,0

|
*FX 249,9

�count=1

�:

�� � �error

�:

�� Save Basic error vector

�?&70=?&202:?&71=?&203

�:

��

�count=count+0.5

�� �

��

�:

�� �error
�:�" at line ";�
:
� Escape stops program
&&� �=17 A%=247:X%=0:Y%=0:� osbyte:�
0#� also removes patch - *FX247,0
:'� �=100 �"Press RETURN";:� � �=13:�
D�
�

00000000  0d 00 0a 24 f4 20 54 72  61 70 20 42 72 65 61 6b  |...$. Trap Break|
00000010  2f 52 65 73 65 74 20 77  69 74 68 20 4f 4e 20 45  |/Reset with ON E|
00000020  52 52 4f 52 0d 00 14 16  f4 20 62 79 20 43 68 72  |RROR..... by Chr|
00000030  69 73 20 44 61 76 69 65  73 20 0d 00 1e 1a f4 20  |is Davies ..... |
00000040  66 6f 72 20 42 42 43 20  61 6e 64 20 45 6c 65 63  |for BBC and Elec|
00000050  74 72 6f 6e 0d 00 28 1f  f4 20 28 63 29 20 41 63  |tron..(.. (c) Ac|
00000060  6f 72 6e 20 55 73 65 72  20 41 70 72 69 6c 20 31  |orn User April 1|
00000070  39 38 35 0d 00 32 05 3a  0d 00 3c 0e 6f 6c 64 76  |985..2.:..<.oldv|
00000080  65 63 3d 26 37 30 0d 00  46 0f 65 72 72 76 65 63  |ec=&70..F.errvec|
00000090  3d 26 32 30 32 0d 00 50  10 6f 73 62 79 74 65 3d  |=&202..P.osbyte=|
000000a0  26 46 46 46 34 0d 00 5a  0b 50 25 3d 26 39 30 30  |&FFF4..Z.P%=&900|
000000b0  0d 00 64 05 5b 0d 00 6e  1a 5c 20 52 65 73 74 6f  |..d.[..n.\ Resto|
000000c0  72 65 20 65 72 72 6f 72  20 76 65 63 74 6f 72 0d  |re error vector.|
000000d0  00 78 14 5c 20 74 6f 20  42 61 73 69 63 27 73 20  |.x.\ to Basic's |
000000e0  ee 20 85 0d 00 82 0e 4c  44 41 20 6f 6c 64 76 65  |. .....LDA oldve|
000000f0  63 0d 00 8c 0e 53 54 41  20 65 72 72 76 65 63 0d  |c....STA errvec.|
00000100  00 96 10 4c 44 41 20 6f  6c 64 76 65 63 2b 31 0d  |...LDA oldvec+1.|
00000110  00 a0 10 53 54 41 20 65  72 72 76 65 63 2b 31 0d  |...STA errvec+1.|
00000120  00 aa 05 5c 0d 00 b4 15  5c 20 69 6e 69 74 69 61  |...\....\ initia|
00000130  6c 69 73 65 20 52 4f 4d  73 0d 00 be 0c 4c 44 41  |lise ROMs....LDA|
00000140  20 23 31 34 33 0d 00 c8  0a 4c 44 58 20 23 31 0d  | #143....LDX #1.|
00000150  00 d2 0b 4c 44 59 20 23  26 45 0d 00 dc 0e 4a 53  |...LDY #&E....JS|
00000160  52 20 6f 73 62 79 74 65  0d 00 e6 0a 4c 44 58 20  |R osbyte....LDX |
00000170  23 32 0d 00 f0 0f 4a 53  52 20 6f 73 62 79 74 65  |#2....JSR osbyte|
00000180  20 0d 00 fa 0a 4c 44 58  20 23 33 0d 01 04 0c 4c  | ....LDX #3....L|
00000190  44 59 20 23 26 46 46 0d  01 0e 0e 4a 53 52 20 6f  |DY #&FF....JSR o|
000001a0  73 62 79 74 65 0d 01 18  05 5c 0d 01 22 1f 5c 20  |sbyte....\..".\ |
000001b0  63 72 65 61 74 65 20 65  72 72 6f 72 20 31 30 30  |create error 100|
000001c0  20 28 42 72 65 61 6b 29  20 0d 01 2c 07 42 52 4b  | (Break) ..,.BRK|
000001d0  0d 01 36 05 5d 0d 01 40  1c 24 50 25 3d bd 28 31  |..6.]..@.$P%=.(1|
000001e0  30 30 29 2b 22 42 52 45  41 4b 22 2b bd 28 30 29  |00)+"BREAK"+.(0)|
000001f0  20 0d 01 4a 05 3a 0d 01  54 1b f4 20 50 6f 69 6e  | ..J.:..T.. Poin|
00000200  74 20 42 72 65 61 6b 20  76 65 63 74 6f 72 20 74  |t Break vector t|
00000210  6f 0d 01 5e 23 f4 20 4d  61 63 68 69 6e 65 20 63  |o..^#. Machine c|
00000220  6f 64 65 20 70 61 74 63  68 20 2d 20 4a 4d 50 20  |ode patch - JMP |
00000230  26 39 30 30 0d 01 68 0e  2a 46 58 20 32 34 37 2c  |&900..h.*FX 247,|
00000240  37 36 0d 01 72 0d 2a 46  58 20 32 34 38 2c 30 0d  |76..r.*FX 248,0.|
00000250  01 7c 0d 2a 46 58 20 32  34 39 2c 39 0d 01 86 0b  |.|.*FX 249,9....|
00000260  63 6f 75 6e 74 3d 31 0d  01 90 05 3a 0d 01 9a 0e  |count=1....:....|
00000270  ee 20 85 20 f2 65 72 72  6f 72 0d 01 a4 05 3a 0d  |. . .error....:.|
00000280  01 ae 1d f4 20 53 61 76  65 20 42 61 73 69 63 20  |.... Save Basic |
00000290  65 72 72 6f 72 20 76 65  63 74 6f 72 0d 01 b8 19  |error vector....|
000002a0  3f 26 37 30 3d 3f 26 32  30 32 3a 3f 26 37 31 3d  |?&70=?&202:?&71=|
000002b0  3f 26 32 30 33 0d 01 c2  05 3a 0d 01 cc 05 f5 0d  |?&203....:......|
000002c0  01 d6 13 63 6f 75 6e 74  3d 63 6f 75 6e 74 2b 30  |...count=count+0|
000002d0  2e 35 0d 01 e0 07 fd 20  a3 0d 01 ea 05 e0 0d 01  |.5..... ........|
000002e0  f4 05 3a 0d 01 fe 0c dd  20 f2 65 72 72 6f 72 0d  |..:..... .error.|
000002f0  02 08 14 f6 3a f1 22 20  61 74 20 6c 69 6e 65 20  |....:." at line |
00000300  22 3b 9e 0d 02 12 05 3a  0d 02 1c 1a f4 20 45 73  |";.....:..... Es|
00000310  63 61 70 65 20 73 74 6f  70 73 20 70 72 6f 67 72  |cape stops progr|
00000320  61 6d 0d 02 26 26 e7 20  9e 3d 31 37 20 41 25 3d  |am..&&. .=17 A%=|
00000330  32 34 37 3a 58 25 3d 30  3a 59 25 3d 30 3a d6 20  |247:X%=0:Y%=0:. |
00000340  6f 73 62 79 74 65 3a e0  0d 02 30 23 f4 20 61 6c  |osbyte:...0#. al|
00000350  73 6f 20 72 65 6d 6f 76  65 73 20 70 61 74 63 68  |so removes patch|
00000360  20 2d 20 2a 46 58 32 34  37 2c 30 0d 02 3a 27 e7  | - *FX247,0..:'.|
00000370  20 9e 3d 31 30 30 20 f1  22 50 72 65 73 73 20 52  | .=100 ."Press R|
00000380  45 54 55 52 4e 22 3b 3a  f5 20 fd 20 a5 3d 31 33  |ETURN";:. . .=13|
00000390  3a f1 0d 02 44 05 e1 0d  ff                       |:...D....|
00000399