BeebEm - BBC Micro and Master 128 Emulator

Built in Debugger

The Debugger is a 6502/Z80/ARM disassembler and monitoring tool. When the debug window is first opened it leaves BeebEm running. Its best to switch off the 'Freeze when inactive' option though otherwise BeebEm will only run when you bring the main window to the front.

Debugger controls:

Break Stops BeebEm running. If currently executing in the OS or ROM area and OS/ROM debug is not enabled then BeebEm will only stop when execution moves out of the OS/ROM. When execution stops the current instruction is displayed.

Continue/Cancel Starts BeebEm running

Trace Shows accesses to the various bits of hardware

Break Breaks execution when the hardware is accessed

BRK instruction Breaks when the BRK instruction is executed

Attach to Host Debugs the host processor

Attach to Parasite Debugs the second processor

Attach to ROM Debugs the ROM code (addresses 8000-BFFF)

Attach to OS Debugs the OS code (addresses C000-FFFF)

Breakpoints Breaks execution when the address hits one of the configured breakpoints

Watches Shows contents of configured memory locations

Execute Command Runs the debug command entered into the command box

To get a list of the debug commands available type ? into the Execute Command box. Notes that all values are specified in hex!

The disassembler shows the following information:

Address OPCodes Instruction A X Y SR Flags

Parasite instructions are shifted right so it easier to follow both host and parasite when debugging tube code.