Edt/Asm is a basic editor with integrated in-memory assembler.  Edt/Asm was

designed so that it could be run from ROM.  The default assembly is at 8000h,

with the text editor buffer at 1000h.  In this configuration programs can be

assembled from 0000h-0FFFh.  There are two ORG addresses in the Edt/Asm source.

The first specifies where Edt/Asm will be assembled, the second one (near the

end of the source file) specifies where Edt/Asm's data begins.  Any memory

below the second ORG value is available for assembled programs.

A restart address is provided 3 bytes above the normal entry point.  The 

restart address resets the baud rate and nothing else.  This entry can be used

either in non-volitile memory systems to recover the current edit buffer, or

can be used by assembly language programs to return control to Edt/Asm without

losing the editor contents.

Editor Commands:

----------------

          A       - Assemble the program

          B       - Move to bottom of buffer

          D       - Move down one line

        ,nD       - Move down n lines

          Itext   - Insert text at current location

         nItext   - Move to line n, then insert text

          I       - Enter multi-line insert mode, end with

         nI       - Enter multi-line insert mode starting at line n,

                    end with

         nG       - Make line n the current line

          K       - Kill (delete) the current line

         nK       - Move to line n, and then delete line

        ,nK       - Kill n lines starting from current line

       n,mK       - Kill m lines starting from line n, n becomes current

          N       - New file - clears buffer

          P       - Print the current line

         nP       - Print line n

        ,nP       - Print n lines starting from current line

       n,mP       - Print m lines starting from line n

          R       - Run program

          T       - Move to top line of buffer

          U       - Move up one line

        ,nU       - Move up n lines

          Q       - Quit to monitor (0F900h, or 08003h on Elf2K)

          V       - Switch to Visual/02 (Pico/Elf only)

Assembler Line Format:

----------------------

label:   OPCODE   ARGUMENTS      ; Comments

Labels and comments are optional, and not all opcodes have arguments.  In 

addition to the 1802 instruction set, Edt/Asm provides 4 pseudo-opcodes:

ORG    addr              Specify address for assembly

DB     b1,b2,...bn       Define a list of bytes in memory

DB     'c1','c2'...'cn'  Define a list of characters in memory. For example, 'A'   or 

DB    ‘This is text’      Is also supported.

DW     w1,w2,...wn     Define a list of words in memory

END    start                End of assembly, also specifies atart address

Where addr,bn,wn  can be a hex value such as 8000h or a decimal value such as 256.

A colon (:) is used to delimit a label.

Example Elf OS restart program

       ORG  2000h      ; start of program (where program will be loaded in memory)

       BR   START      ; branch around header

       DB   8Ch        ; the 12th month of year with upper bit set on to indicate extended header

       DB   25         ; the 25th day of the month

       DW   2020       ; the year

       DW   2            ; indicate that this is build 2 of the program

       DB   'M','R'    ; add some text for the Elf OS version command to display

       DB   0            ; indicate end of ASCIIZ text string

START: LBR   0FF00h    ;Elf-OS restart.  Diskless return to EDTASM  is 0B003h

       END  START      ; indicate the entry point for the program      

  NOTE: A hex address  or constant beginning with A-F must have a leading zero.

Edt/Asm currently only supports simple arguments, arithmetic expressions

cannot be used.  When specifying registers, the register number may (but need

not) begin with R, for example:    LDN    R8

The high byte of a value can be obtained by adding .1 to the end of a label,

for example:    LDI    STACK.1     will load the high byte of the address of

STACK.  .0 will obtain the low byte of a value, for example:   LDI   STACK.0