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Chapter 4: Viewing Code and Data
Using Simulated I/O
Display and Keyboard
The debugger provides a window named stdio which functions as the normal
display output for target programs. The screen can be opened for output from
target programs via SIMIO with the special name /dev/simio/display. This
name appears to be an UNIX file name. However, it is really a name reserved
by the debugger to indicate the internal screen. The keyboard is accessed by
the special name /dev/simio/keyboard.
UNIX Files
UNIX files are accessed by their names from the target program running in
the debugger in the same way they are accessed by host software. The file
operations of open, close, read, write, and seek are supported by the SIMIO
protocol. When opening a stream on an UNIX file, SIMIO supports the same
control parameters for file creation and blocking I/O that are available to host
programs.
UNIX Processes
UNIX processes can be run as subprocesses to the debugger with their input
and output directed to the user program. Subprocesses are controlled from the
user program by a Process Identification number (PID). This lets the user
program check specific subprocesses, send them signals, or stop them. This
subprocess facility allows user programs to take advantage of the powerful
software and execution environment of the host UNIX system. Host programs
can be used to process data for a debugger user program or to simulate
portions of the software that are not available in the user program.
Because simulated I/O lets the debugger execute UNIX commands, the
debugger can communicate with other host system I/O devices, such as
printers, plotters, modems, etc.
For more information on using UNIX processes, refer to the description of
the exec_cmd() function in the "Environment Dependent Routines" chapter of
the Motorola 68000 Family C Cross Compiler User's Guide.
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