1. Introduction

1.1 Features

• Simulation of 6801/6301, 6805, and 6811 series processors
• ROM like monitor with one/two character commands (Motorola style)
• Breakpoints in code and data
• Disassembler
• Global symbol table (formats generated by ASLINK and FASM)
• On chip I/O partially simulated (SCI, SPI, single timer output compare)
• 64K memory model
• Easy for user to add code simulating IO peripherals. A couple of examples included (including an I2C like device, Xicor X9241).
• Runs many example test programs, including monitors. A rather comprehensive 6800 test program from the 6800 user group archive on Motorolas FTP site (http://www.mot.com/sps/mcu/usrgroup) has been successfully run on the simulator.
• Performance. When compiled with gcc and inlining, the simulator runs at
  • 486DX33 w/64kb cache
  • 0.15 the speed of an 8Mhz 6811 (2Mhz internal clock)
  • 0.4 the speed of an 2.4576 Mhz 6301 (0.6144 Mhz internal clock)
  • Pentium 133
  • 0.5 the speed of an 8Mhz 6811 (2Mhz internal clock)
  • 1.0 the speed of an 2.4576 Mhz 6301 (0.6144 Mhz internal clock)

1.2 Future

The following is a list of features that may be added to sim68xx in the future.

Graphical window user interface

Candidates to concider:

• Tcl/Tk (tksim68xx). Will run under Unix, MS Windows and Mac. Windows and commands have already been designed using the vtcl GUI builder (vtcl).
• Java AWT (jsim68xx). Standalone or applet. Will run on Unix, MS Windows, OS/2 and Mac.
• WxWindows. Will run under Unix, MS Windows and Mac.
• V. Will run under Unix, MS Windows (later OS/2 and Mac)
• YACL. Will run under Unix, MS Windows, OS/2 and Mac.

Character window user interface

Candidates to concider:

• Xview (sim68xxtool). Will run under Unix variants supporting Open Windows, for example Sun, Linux, AT&T.
• Turbo Vision (tvsim68xx). Will run under MSDOS, OS/2 and Unix (at least Linux), but not native MS Windows.

Symbolic C debugging

This requires that symbol and line number information is available, either in the executable file or in a separate file. Which symbol format that will be supported, has to be defined. The ASLINK and FASM assemblers that are support global symbols only.

Remote debugging, where the simulator communicates with a symbolic debugger over a serial line (simulated or real line), is another possible solution. It is quite attractive in the way that the debugger is completely independent of the simulator. The GNU debugger, GDB, for example, has defined a protocol to debug using a serial line. GDB can use this protocol to read from and write to memory adresses.

Dynamic Linking for simulating on-chip and external IO

The current design requires that code for simulating IO is separately compiled, and statically linked into the executable, even though the simulator calls the IO through a function pointer.

1.3 Revision history

• 1996-08-03/AR. Created document skeleton.
• 1996-08-03/AR. Wrote IO chapters with unfinished example.
• 1999-08-20/AR. Completed. Collected info from many small files.