Atari 400 Technical Reference Manual page 279

ERR LINE
ADDR Bl B2 B3 B4
CENTRAL INPUT/OUTPUT (CIO) 2-7-79 PAGE 18
807
. PAGE
808
809 ;
CIa LOCAL RAM <USES SPARE BYTES IN ZERO PAGE IOCB>
810 002C ENTVEC
= ICSPRZ
811
812 ;
CIa MAIN ROUTINE
813
814
i
CIa INTERFACES BETWEEN USER AND INPUT/OUTPUT DE
815 E4C4 85 2F
CIa: STA C IOCHR
iSAVE POSSIBLE OUTPUT CHARACTER
816 E4C6 86 2E
STX ICIDNO iSAVE IOCB NUMBER
*
N
817
818 ;
CHECK FOR LEGAL IOCB
819 E4C8 8A
TXA
820 E4C9 29 OF
AND i$F
i
IS IOCB MULTIPLE OF 16?
821 E4CB DO 04
BNE CIERRl
i
NO, ERROR
822 E4CD EO 80
CPX
#MAXIOC
i
IS INDEX TOO LARGE?
823 E4CF 90 05
BCC IOCl
i
NO
824
825
INVALID IOCB NUMBER -- RETURN ERROR
826
E4Dl AO 86 C IERR1: LDY
iBADIOC
i
ERROR CODE
827
E4D3 4C lB E6 JMP
CIRTNl
i
RETURN
828
829
i
MOVE USER IOCB TO ZERO PAGE
830 E4D6 AO 00
IOCl : LDY #0
831 E4D8 BD 40 03
IOC1A: LOA IOCB,X
i
USER IOCB
832 E4DB 99 20 00 STA
IOCBAS,Y
j
TO ZERO PAGE
833 E4DE E8 INX
834 E4DF C8
INY
835 E4EO CO OC
CPY i12 ; 12 BYTES
836
E4E2 90 F4 BCC
IOC1A
837
838
COMPUTE CIa INTERNAL VECTOR FOR COMMAND
839 E4E4 AO 84
LOY iNVALID iASSUME INVALID CODE
840 E4E6 AS 22
LDA ICCOMZ
iCOMMAND CODE TO INDEX
841 E4E8 C9 03 CMP
#OPEN
i
IS COMMAND LEGAL?
842 E4EA 90 25 BCC CIERR4
i
NO
843
E4EC A8 TAY
844
845
MOVE COMMAND TO ZERO BASE FOR INDEX
846 E4ED CO OE
CPY iSPECIL
i
IS COMMAND SPECIAL?
847 E4EF 90 02 BCC
IOC2
i
NO
848 E4Fl AO OE LDY #SPECIL
i
YES, SET SPECIAL OFFSET INDEX
849
E4F3 84 17 IOC2: STY ICCOMT
iSAVE COMMAND FOR VECTOR
850 E4F5 B9 C6 E6
LOA COMTAB-3,Y
iGET VECTOR OFFSET FROM TABLE
851 E4F8 FO OF BEG
CIOPEN iGO IF OPEN COMMAND
852
E4FA C9 02 CMP
#2 i IS IT CLOSE?
853
E4FC FO 35 BEG
CICLOS ; YES
854 E4FE C9 08
CMP #8 i IS IT STATUS OR SPECIAL?
855 E500 BO 4C
BCS CISTSP
; YES
856 E502 C9 04
CMP #4 i IS IT READ?
857 E504 FO 63 BEG
CIREAD
i
YES
858 E506 4C C9 E5 JMP
CIWRIT i ELSE, MUST BE WRITE