This Technical Note documents the commands the Apple II Parallel Interface Card's firmware supports and how to find the slot occupied by an Apple II Parallel Interface Card.
The manual that shipped with the Apple II Parallel Interface Card states correctly that its firmware can be "identical to the firmware in the earlier Apple II Centronics(R) Printer Card" or that it can be "identical to the firmware in the earlier Apple II Parallel Printer Card." However, the manual did not correctly document the commands the Parallel Interface Cards can handle or explain the commands clearly.
Apple II Parallel Interface Card commands, embedded in the output flow to the card's firmware, are invoked by the BASIC output routines. The following three options affect the output data flow and can be controlled by sending control codes as commands to the firmware:
Note: When an Apple II Parallel Interface Card in Parallel Printer mode is echoing characters to the video screen, the line length is forced by the card's firmware to 40.
Note: The automatic line-feed option can only be used when the Apple II Parallel Interface Card is in Parallel Printer mode.
All commands are preceded by a command character. The normal command character is Control-I (ASCII $09). If you want to change the command character from Control-I to another command character (for example, Control-W), send Control-I, Control-W. To change back, send Control-W, Control-I. The format of the commands is as follows:
{command-character} {command-string}
There are two types of commands:
In Centronics Printer mode, the default settings are:
The Centronics mode firmware does not support the option to automatically generate line-feed characters after carriage return characters. When the interface card is initialized in Centronics mode, it also sends the Centronics MicroPrinter 40-column mode control character to the printer (ASCII $9E).
The following are the commands supported by the Apple II Parallel Interface Card when it is in Centronics Printer mode:
In Parallel Printer mode, the default settings are:
The following are the commands supported by the Apple II Parallel Interface Card when it is in Parallel Printer mode:
The Apple II Parallel Interface Card manual does a good job of describing the Apple Pascal 1.1 interface standard. However, publishing that information in that manual is very misleading since the Apple II Parallel Interface Card does not support any part of the PascalÊ1.1 interface standard.
However, since most programs use the Pascal 1.1 device signature bytes to identify peripheral cards, here are the values you find in the Pascal 1.1 device signature byte addresses:
Remember, these values do not correspond to any signature bytes defined by the Pascal 1.1 interface standard. The address $Cs0B contains the value $58 and the address $Cs0C contains the value $FF, (the last two bytes of a JSR $FF58 to identify the slot) but these two locations should not be used to identify parallel cards in general.
This and all of the other Apple II Technical Notes have been converted to HTML by Aaron Heiss as a public service to the Apple II community, with permission by Apple Computer, Inc. Any and all trademarks, registered and otherwise, are properties of their owners.
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