Description: Apple II+ Mini-Assembler (1 of 4)
Header: Apple II+ Mini-Assembler (1 of 4)


 This article last reviewed: 21 September 1984

 The attached listing is a relocated version of the mini-assembler for the
 Apple II+ with instructions for the Apple II version.  This version can be
 BRUN from the disk or BLOADed and start with CALL 2048 from Applesoft.  To
 restart use CAll 2051.  From machine language the start is 800G and the
 restart is 803G.  Users who have Integer Basic available need only enter that
 language and use the instructions in part one of this note.

 Please note that the mini-assembler performs a NEW command, so it will wipe
 out any resident Applesoft program.  Also note that the mini-assembler loads
 from $800 to $947.  Don't try to assemble anything into those locations.

 This note covers the operation of the mini-assembler only.  It is not a course
 in assembly language programming.  For a reference on programming the 6502
 microprocessor, refer to the Synertek Programming manual or any of the
 tutorials available. This note assumes the user has a working knowledge of
 6502 programming and mnemonics.

 The mini-assembler is a programming aid aimed at reducing the amount of time
 required to convert a handwritten program to object code.  The mini-assembler
 is basically a look-up table for opcodes.  With it, you can type mnemonics
 with their absolute addresses, and the assembler will convert it to the
 correct object code and store it in memory.

 Typing "F666G" puts the user in mini-assembler mode.  While in this mode, any
 line typed in will be interpreted as an assembly language instruction,
 assembled, and stored in binary form unless the first character on the command
 line is a "$".

 If the first character of a command line is a "$", the remainder of the line
 will be interpreted as a normal monitor command, executed, and control
 returned to the mini-assembler.  To get out of the mini-assembler, press
 RESET.

 If the first character on the line is blank, the assembled instruction will be
 stored starting at the address immediately following the previously assembled
 instruction.  If the first character is not a blank nor a "$", the line is
 assumed to contain an assembly language instruction preceded by the
 instruction address (a hex number followed by a ":").  In either case, the
 instruction will be retyped over the line just entered in dis-assembler format
 to provide a visual check of what has been assembled.

 The counter that keeps track of where the next instruction will be stored is
 the pseudo PC (Program Counter) and it can be changed by many monitor commands
 (eg.  'L', 'T', .  .  .). Therefore, it is advisable to use the explicit
 instruction address mode after every monitor command and, of course, when the
 mini-assembler is first entered.

 Errors (unrecognized mnemonic, illegal format, etc.)  are signalled by a
 "beep" and a caret ("^") will be printed beneath the last character read from
 the input line by the mini-assembler.



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