ruud.baltissen_at_abp.nl
Date: 2008-02-26 07:33:51
Hallo Spiro,
This is the piece of code from the 1541:
L_C245 cpx F1CNT ; ',' after '=' ?
beq L_C24C ; no, ->
ora #$04 ; set bit 2
L_C24C ora #$03 ; set bit 0 and 1
eor IMAGE
sta IMAGE ; flag syntax test
L_C254 lda IMAGE
ldx INSTRU
and TblSyntax-8,X ; combine with checkbyte
==> ^^^^^^^^^
bne L_C260 ; faulty syntax, ->
rts
L_C260 sta ERWORD ; set error flag
lda #$30
jmp OutputErrorMsg ; 30, 'Syntax error'
Tabel found at $FEAD:
;** Bytes for syntax check
TblSyntax .by $51, $DD, $1C, $9E, $1C
;
; ^ ^
; | |
; +-------------------+---- why are these here?
I found out that $1C is used by the directory command:
;** Load directory
[DA55]
J_DA55 lda #$0C ; command number 12
sta INSTRU
12 - 8 = 4, $51 is at the 4th place. No misunderstanding here IMHO
The $51 should be used for the COPY command IMHO. But there is a
problem, the table:
;** Table of command words
[FE89]
TblCommands
.by "V" ; Validate
.by "I" ; Initialize
.by "D" ; D (back up, not used)
.by "M" ; Memory
.by "B" ; Block
.by "U" ; User
.by "P" ; Position
.by "&" ; USR execute
.by "C" ; Copy
.by "R" ; Rename
.by "S" ; Scratch
.by "N" ; New (Format)
shows that Copy is at place 8. So "TblSyntax-8" will point to $51 IMHO.
But:
ldx #$0B ; strat with New command
L_C16A lda TblCommands,X ; compare commands
cmp CHAR ; with char
beq L_C17A ; found, ->
dex
bpl L_C16A
lda #$31 ; NOT found
jmp OutputErrorMsg ; 31, 'syntax error'
L_C17A stx INSTRU
===> cpx #$09 ; commandnumber < 9 ? <===
bcc L_C184 ; yes ->
jsr ChkSyntax ; test for R, S or N
L_C184 ldx INSTRU ; X = commandnumber
At the place marked with ===> the value 8 is ruled out for a syntax
check IMHO. Or am I wrong ???
--
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