s8x30x - Disassembler for Signetics 8X300/8X305

Copyright 2016 Eric Smith spacewar@gmail.com

s8x30x development is hosted at the s8x30x Github repository.

Introduction

Western Digital's earliest hard disk controllers were board-level products based on the Signetics 8X300 or 8X305 bipolar processors.

s8x30x provides a disassembler for the 8X300/8X305.

s8x30x was developed to support reverse-engineering and modification of the firmware of the Western Digital WD100x family of disk controllers, and consequently some features that would be of use for general purpose 8X300/8X305 support are not present.

Syntax

The output of the disassember is in a custom syntax that does not match the Signetics MCCAP assembler, or any other existing assembler. It is intended that an assembler be added to the s8x30x package in the future.

Bit positions are designated with bit 0 as the least significant bit and bit 7 as the most significant bit, which is the opposite of the notation Signetics uses, but matches almost everything else using microprocessor and peripheral chips, including the I/O on the WD100x disk controllers.

The syntax for source and destination registers and I/O ports incorporates the length and rotation fields.

• When an entire register is used without rotation or length, it is represented as just the register name, e.g., r5.

• When an entire register is used with rotation, it is represented as the register name with a right rotation operator, e.g., r5>>>3.

• When an entire I/O port is used as an operand, it is by default represented as sliv or sriv for left or right I/O ports as a source, and dliv or driv for left or right I/O ports used as a destination. The fast I/O select decoding, if used, may substitute the I/O port names.

• When a single bit of an I/O port is used as an operand, it is represented as the I/O port name subscripted by a bracketed bit number, e.g., sliv[7] for the most significant bit of the source left I/O register.

• When a range of bits of an I/O port are used as an operand, they are represented as the I/O port name subscripted by a bracketed bit range, witht he leftmost and rightmost bit numbers separated by a colon, e.g., sriv[3:0] for the least significant four bits of the source right I/O register.

Disassembler limitations

As of this writing, the output of the disassembler has not been reassembled with any assembler, so it's possible and even likely that there are bugs resulting in inacurate disassembly.

Disassembler usage

The dis8x30x disassembler can accept either raw binary input files (default), or Intel hex format input files if the --hex option is given on the command line. If other file formats are needed, the srec_cat utility of srecord is recommended.

At least two input files are required. The first and second input files are the most significant and least significant byte of the 8X30x instruction. Any further input files provide fast select data, used by hardware other than the 8X30x processor.

The -l option causes the disassembler output to be generated in a format similar to an assembler listing file, with the address and object code for each disassembled instruction to the left of the disassembled instruction.

The --wd1000 and --wd1001 options select fast I/O select decoding for the Western Digital WD1000 and WD1001 controllers, respectively.

Disassembler examples

The examples of command lines given below do not show the path to the executable, nor, for operating systems that require it, the explicit specification of the Python interpreter.

• dis8x30x --wd1000 msb.bin lsb.bin fast.bin >wd1000.dis

  Disassembles from three raw binary files, uses WD1000 fast I/O decode, and generates output in the form of assembly source

• dis8x30x --wd1001 -l --hex msb.hex lsb.hex fast.hex >wd1001.dis

  Disassembles from three Intel hex files, uses WD1001 fast I/O decode, and generates output in the form of a listing.

License information

This program is free software: you can redistribute it and/or modify it under the terms of version 3 of the GNU General Public License as published by the Free Software Foundation.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.