ROM Monitors / Debuggers

These provide a monitor program running on your target board that implements a debugging environment.In general they rely on a communications connection between the target board and the PC. In it's simplest form this is the built-in serial port of the microcontroller but other options may be available. Code to be debugged can be downloaded via this communications link to RAM on the target (replaced by ROM in the final product). As the code is now in RAM software breakpoints (typically software interrupts) may be inserted and a small monitor can service these requests using the communications link to inform the operator of the values held in registers, variables etc.

These programmers come into their own once a board is up and running (they need CPU, ROM, RAM and a UART, all to be working) and are a good low cost alternative to ICE for much software development.

A great deal of ingenuity has gone into hardware and software to support the many different products in this group and each has it's own strengths and weaknesses.

The merits of each will depend on your needs. So here is a brief sketch of the technique and facilities provided by the products COMSOL has available.

HI-TECH,Avocet

these C compilers come with a small program that links to a simple DOS, text based debug monitor. Use the monitor to query or change global variables, single step the code or set breakpoints.

Cosmic, IAR, Keil

The monitor from these link to a more sophisticated windows based application on the PC that normally looks like the C manufacturers chip simulator.

Paradigm C++

A custom version of the Borland Turbo Debugger that runs on a PC while linked to a target 8086/186. Runs Borland, Microsoft and Watcom C and C++.

VP Remote Debug

Beacon Technology Visual Probe - used to be known as SSI, this powerful PC windows based debugger links to a 4 K monitor on an embedded target and provides full ICE like features for real mode 386 applications programmed in Microsoft, Watcom or Metaware C and C++.

chipFORTH

Monitor is only 256 bytes (no we did not miss a decimal point) this provides the fully interactive development much beloved by FORTH aficionados. Uses the serial port built into the microcontroller but cleverly re-directs target UART output to the PC's screen.

Grammar Engines

A ROM emulator with a built-in serial channel. Not by itself a monitor, but support is available to use its serial channel instead of the standard (but often unavailable) UART to link to a number of popular monitors including Paradigm for 8086/186, SSI (Now Beacon Technology) for 386,  X-Ray for 68000 and the GNU debugger.

Freescale BDM/SDI

Hardware on the 68HC12, HC16, CPU32, MCORE, ColdFire and Power PC processors uses a small number of pins to communicate with built-in debug facilities on the chip. Abatron supply some very fast interfaces using this technique and P & E provide a very low-cost solution.  Many of the 68HC08 chips include an on chip monitor MON08 and P&E's MON08 board interfaces to it both for development and programming purposes.

JTAG

Like BDM/SDI this requires specific hardware support on the chip. JTAG provides a mechanism for testing and programming complex parts such as PLDs and Flash memories in situ. It looks like it's the way ICE support is going to go as CPUs get faster and more complex while bondout chips are just not available. Abatron and iSYSTEMS iC3000 both provide JTAG ports for PPC and ARM. 

CMX - Bug

A utility supplied with CMX, it uses a task running a serial port link to a PC to monitor and change the settings of applications tasks while they are running.

CMX-Tracker

A CMX option that logs all calls to the real-time executive and then allows a task , that talks to a PC via a serial port, to review details of the task interactions.