MICROPLAN                                         MML Ltd.
=========                                        11 Sun Street
                                                 London E.C.2.
                                                 Tel: 01-247 0691
COPYRIGHT JULY 1980

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			DIS
			===

Program DIS disassembles a .COM file into a .DIS file which may be
subsequently assembled.
The DIS file has the following features:
1.	All branch points are provided with a label
2.	Where permitted data blocks are split into DB, DW & DS
3.	All references before 0100H and after program are
	EQUATE statements
4.	Any unresolved block commences with a U type label

INSTRUCTIONS
------------

The program is run by entering
A>DIS filename

The program forces type .COM for the source filename
and writes dissasembled mnemonics to file type .DIS.
The program checks for non-existance of .DIS file type.

The program then requests for additional program entry points
DIS assumes that the first entry is at 0100H.

FIRST PASS
----------

In the first PASS enter 0000 and DIS will disassemble the file

In most files DIS is unable to resolve all of the .COM code and
in particular it cannot resolve the PCHL instruction.
All unresolved code will be given a label starting with a U,
and the code will be listed as a block of data.  Armed with a
list of mnemonics you should be able to establish if this unresolved
data is actually program code.

Examine the listing and see if you can decode the unresolved
areas, then destroy the .DIS file and run DIS again.

SECOND & SUBSEQUENT PASSES
--------------------------

On the second and subsequent passes, you may assist the disassembly
by entering the additional program entry points when
requested.  You may also notify DIS of other types of
code by preceeding the address with one of the folloing:

1.	P	Progam entry point (default)
2.	N	Data numeric entry point
3.	W	Data word address
4.	T	Data table of program jump address

The last type (T) is normally used by a PCHL instruction in
using a lookup table. It assumes the table is contiguous words
of program entry points.

Example
ADD ENTRY POINT (0000 TO QUIT): 02DA
ADD ENTRY POINT (0000 TO QUIT): T2F8C
ADD ENTRY POINT (0000 TO QUIT): 0000

ERRORS
------

A) FATAL ERRORS
   A fatal error occurs with an ERROR message on the terminal and
   the program terminates.
   This is normally caused by an eroneous instruction in the
   ADD ENTRY POINT address
   The solution is to recheck your entry points and re-run after
   erasing the .DIS file

B) SYNTAX ERRORS
   Other errors occur when there is a conflict between address
   references.  The .DIS file is marked with an ERROR message.
   Minor conflicts result in a WARN message.


ASSEMBLY SOURCE CODE
--------------------

Finally when you have resolved all blocks of the code,
PIP an .ASM file.

Using the editor check for the following:

1.	Any ERROR or WARN message produced by DIS
2.	Check if LXI instruction is referencing
	a) address (default)
	b) constant
	In the latter case change the address to a constant

The .ASM file is now suitable for modification

For use in MPM, the DIS produces the BASE bias for relocation
at a different address, and so long as all the constants in 2b
above have been resolved, the .ASM file can be used to produce
a reliable page relocatable file.

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