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%OP%HE\%H2%Z88 Users' Club Software Library%H2%\
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%OP%DE\\Z80 DISASEMBLER (Z80DIS V2.1) MANUAL\\
%CO:A,72,70%%C%%H1%%H2%Z80 DISASSEMBLER V2.1


The Z80DIS V2.1 can disassemble any code into Z80 mnemonics at any 
memory location and with any bank arrangement. It will also display, 
at option, Z88 operating system codes which follow a "RST 18H" or a 
"RST 20H" instruction - these codes are listed in the "Z88 Software 
Developers Notes" (published by Cambridge Computer Ltd). Disassembly 
can be directed to the screen or a device.

Z80DIS V2.1 is in two parts - the BASIC driving program and the 
machine code routine. The machine code is located at &37C9 so that 
Z80DIS V2.1 may be used on both the expanded and unexpanded machine 
(i.e. less than 128K RAM in slot 1).

The machine code is stored in the file "Z128C". If this file's name 
is to be changed then line 110 of the BASIC program must be altered 
so that it uses the new file name to load it up.

On loading and running the BASIC program the user will be presented 
with the main menu. Pressing the appropriate key will give the user 
access to the commands which are examined in detail below.


%H2%A. DISASSEMBLE TO SCREEN

This command disassembles code to the screen, as prescribed by the 
parameters given in the right-hand window. Z80DIS V2.1 will scroll 
the disassembley on to the screen using a split screen arrangement so 
that 24 lines can be displayed at once. The disassembley may be 
paused at any moment by pressing the left hand SHIFT and <> keys 
together.


%H2%B. DISASSEMBLE TO A DEVICE

Code is disassembled, as above, but to a device. By default the 
device is ":PRT.0", which is to a printer, controlled by the 
parameters set by PrinterEd. Other devices may be used and a list is 
given below:

:RAM.0, :RAM.1, :RAM.2, :RAM.3, :RAM.-, :NUL.0, :COM.0

Refer to the "Z88 USER GUIDE" for more details.

Sending the disassembly to a file in RAM will allow PIPEDREAM to load 
it up, as plain text, so that it may be edited.


%H2%C. CONTINUE DISASSEMBLY TO SCREEN

If disassembly was aborted then it can be continued to the screen by 
selecting this command, regardless of whether disassembly was to the 
screen or a device.
                                      
%P0%
The user has the option of continuing the disassembly from the 
aborted address, by pressing "ENTER", or providing Z80DIS V2.1 with a 
new address to continue from. The latter will not affect the START 
address parameter (see later) and is therefore useful if the user 
wishes to branch away from the main disassembly, to disassemble 
another piece of code in the memory, and then later revert back to 
the original disassembly by using command "A) Disassemble to the 
SCREEN", described above.

In each of the above cases the "ESC" key will abort the disassembly 
and return Z80DIS V2.1 to the main menu.


%H2%D. EXIT TO BASIC

This simply stops the program and returns the control of the Z88 to 
BBC BASIC(Z80).


The disassembler parameters determine the way in which Z80DIS V2.1 
performs the disassembly and may be altered as follows.


%H2%0 - 3. ALTER MEMORY BANK ARRANGEMENT

On running, the current bank arrangement is used as default for the 
initial memory bank arrangement. Other pages of memory can be 
selected for each bank by pressing "0" - "3". The memory will be set 
up by Z80DIS V2.1 using this specified arrangement, which would be 
the memory banks the Z80 microprocessor would use if it were to read 
from a memory location.
                                                   
Bank pages are of 16K in size and a summary follows of the meaning of 
each page value give to Z80DIS V2.1. For more information of how the 
memory works either read the "Z88 Software Developers Notes" or the 
article by Mark Stevenson on page 2.5.20 of "Z88 Eprom" (Sept-Oct 
1988 edition).


%H1%PAGE VALUE%H1%  %H1%MEANING%H1%

 &00-&1F    Z88's internal ROM (only pages &00-&07 are used by the Z88).
 &20-&3F    Z88's internal RAM (only pages &20-&21 are used by the Z88).
 &40-&7F    Memory pages of the card in Slot 1 (under the keyboard).
 &80-&BF    Memory pages of the card in Slot 2.
 &C0-&FF    Memory pages of the card in Slot 3.


%H2%4. TOGGLE Z88 OPERATING SYSTEM CODES OPTION

Toggling the status of the option will decide whether Z80DIS V2.1 
will use the "DEFB" directive to display Z88 operating system codes 
which are used by the Z88 to invoke special operating system routines 
when it executes a "RST &18" or a "RST &20" instruction. These codes 
are listed in the "Z88 Software Developers Notes".

%H2%5. ALTER DISASSEMBLY START ADDRESS

This simply allows a location in logical memory, from which Z80DIS 
V2.1 disassembles from, to be entered. 


%H2%6. ALTER DISASSEMBLY END ADDRESS

This allows a location in logical memory, at which the disassembler 
stops disassembling when reached, to be entered.

Note that all input is expected to be in hexadecimal. If, however, 
should values need to be given in decimal then the ampersand ("&") 
can be deleted from the input line to allow this.



Z80DIS V2.1 is for free distribution among members of the Z88 Users' 
Club and is not to be sold for profit making purposes without the 
prior written consent of the author.




Keith R Rickard  7.10.1990.                        85 Havelock Road
                                                   Dartford
                                                   Kent  DA1 3HZ.