TRS-80 Emulators for Windows and MS-DOS

Matthew Reed's emulators, utilities, and development tools for TRS-80 Models 1/3/4

Z80Disasm — A TRS-80 Disassembler for Microsoft Windows

Z80Disasm is a freeware command-line Z80 disassembler for Windows. It is a symbolic labeling disassembler that supports all Z80 instructions and can read either TRS-80 CMD files or Intel HEX files.

The Z80Disasm command line looks like this:

Z80DISASM [options] [file]

The following options are supported:

-v:<file> Read file from a TRS-80 virtual disk instead of a Windows directory.
-s:<file> Use <file> as a screening data file.
-o:<file> Write disassembly to <file> instead of screen.
-r Don’t generate symbolic labels during disassembly.

For example, to disassemble the program SCRIPSIT.CMD to the screen, the command line would look like this:


To disassemble the program ROBOT.CMD to the file ROBOT.ASM, using the screening file ROBOT.SCR, the command line would look like this:


To disassemble the program VC/CMD which is contained on VISICALC.DSK, the command line would look like this:


Screening files

Z80Disasm supports the use of screening files to separate data from code. By using a well designed screening file, data areas can be properly marked using DB and DW pseudo-ops instead of meaningless instructions.

A screening file follows a well-defined format, consisting of address ranges separated by commas. (Long time TRS-80 users may remember this format as similar to that used by DSMBLR, the MISOSYS disassembler for the TRS-80.)

Four different types of address ranges are supported:

aaaa one byte at aaaa
bbbb-cccc a range from bbbb to cccc
-dddd a range from 0x0000 to dddd
eeee- a range from eeee to 0xFFFE

Two types of prefixes are supported for ranges:

$ identify as byte data (the default)
# identify as word data

For example, here is a valid (albeit meaningless) sample screening file:


That screening file indicates the following areas of data:


Z80Disasm is freeware, but remember that it is not public domain software. All copyrights connected with the program and its accompanying document files remain with me (Matthew Reed).

Z80Disasm is a Windows console application.