6502/cc65
1
0
Fork 0
mirror of https://github.com/cc65/cc65.git synced 2024-12-27 00:29:31 +00:00
Code Issues Projects Releases Wiki Activity

Improved device I/O under DOS 3.3

Browse Source 
Certain scenarios (e.g. not running any Applesoft program at all since booting DOS 3.3) can make DOS 3.3 consider cc65 device input (e.g. getchar()) that reads a CR interpreting the command in the keyboard buffer. Setting the hibyte of the Applesoft currently executed line number to some value <> $FF (beside setting the input prompt to some value <> ']') makes DOS 3.3 understand that we're not in intermediate mode and that therefore I/O not preceded with ctrl-d mustn't be fiddled with (see DOS 3.3 routine at $A65E).
This commit is contained in:
Oliver Schmidt 2020-12-19 19:54:12 +01:00
parent 59c58acbe3
commit 0f4cb443b4
2 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
asminc/apple2.inc
View File

@ -15,6 +15,7 @@ PROMPT := $33 ; Used by GETLN
RNDL := $4E ; Random counter low
RNDH := $4F ; Random counter high
HIMEM := $73 ; Highest available memory address+1
CURLIN := $75 ; Current line number being executed
;-----------------------------------------------------------------------------
; Vectors

9
libsrc/apple2/read.s
View File

@ -19,11 +19,14 @@
.segment "ONCE"
initprompt:
; Set prompt <> ']' to let DOS 3.3 know that we're
; not in Applesoft immediate mode and thus keep it
; from scanning our device I/O for DOS commands.
; Set prompt <> ']' and currently executed Applesoft
; line number hibyte <> $FF to let DOS 3.3 (at $A65E)
; know that we're not in Applesoft immediate mode and
; thus keep it from scanning our device I/O for DOS
; commands.
lda #$80 ; Same value used at $D52C
sta PROMPT
sta CURLIN+1 ; Any value <> $FF will do
rts
.code