TITLE
Apple III: Emulation Mode - Controlling Bit 8 of the RS-232 Port 

Article ID: 19
Created: 9/21/84
Modified: 10/29/84
 

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TOPIC 


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DISCUSSION 

This driver allows the user to control bit 8 of the built-in RS-232 port in
Emulation Mode.  Bit 8 is used by some printers to select expanded or normal
print mode or to enable alternate or graphics character sets.  DOS 3.2 or DOS
3.3 is required to use this routine.  Both the Serial Card Emulation and the
Communications Card Emulation are supported.

SOFTWARE ENTRY

Boot a DOS diskette and enter the monitor with CALL -155 and type

       3B0:A9 07
       :20 95 FE
       :A9 80
       :20 ED FD
       :A9 C5
       :85 36
       :A9 03
       :85 37
       :4C EA 03
       :29 7F
       :0D CD 03
       :4C 07 C7
       :80

To check your typing, type

       3B0L

and compare your listing to the one below.

       03B0-   A9 07       LDA   #$07
       03B2-   20 95 FE    JSR   $FE95
       03B5-   A9 80       LDA   #$80
       03B7-   20 ED FD    JSR   $FDED
       03BA-   A9 C5       LDA   #$C5
       03BC-   85 36       STA   $36
       03BE-   A9 03       LDA   #$03
       03C0-   85 37       STA   $37
       03C2-   4C EA 03    JMP   $03EA
       03C5-   29 7F       AND   #$7F
       03C7-   0D CD 03    ORA   $03CD
       03CA-   4C 07 C7    JMP   $C707
       03CD-   80          ???

Now return to Basic with 3D0G

SAVING THE PROGRAM TO DISK:

Save the driver to disk by typing

       BSAVE SERIAL DRIVER, A$3B0, L$1E

USING THE PRINTER:

The driver should be in memory before you want to use the printer.  You must
load the driver and initialize the interface.

From command mode type

       BLOAD SERIAL DRIVER
       CALL 944

This may be done from a program by entering

       100 PRINT D$;"BLOAD SERIAL DRIVER" : CALL 944

assuming that D$ contains a CTRL-D.

If you want to switch back to the video monitor for output type

       PR#0

or in a program enter

       200 PRINT D$;"PR#0"

Then to reconnect the printer, all that is required is

       CALL 954

or from a program

       300 CALL 954

SETTING THE PRINT MODES:

To set normal print mode POKE 973,0
To set expanded print mode POKE 973,128