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If you think ROM emulators are the same old ho-hum sort of product they've always been, you might want to take a second look. The ROM emulator companies have been getting pretty creative. They don't just emulate memory anymore. After looking at the advanced features of some of these ROM emulators, you might even want to consider buying one of these instead of an in-circuit emulator.

You don't have to go very far to find ROM emulators with features including trace capability, hardware breakpoints and watchpoints, and code coverage analysis. Of course, to use these great features, you'll want to use the ROM emulator with a remote target debugger. (Also known as a ROM monitor debugger.)

Unfortunately, remote target debuggers require a communications channel for the monitor to talk to the debugger on the host system. In some applications, especially small 8-bit applications, this squandering of a UART channel can rule out a remote target debugger as a viable debugging solution. Fortunately, ROM emulators provide a solution—the Virtual UART. A Virtual UART is a UART mapped into the emulated address space. The ROM emulator usually has an API, which allows the virtual UART to be "written" to with read cycles since the ROM emulator is usually emulating read-only memory. Most ROM emulator companies provide a Virtual UART as an option to their ROM emulators. And, one vendor, Applied Microsystems, even offers a Virtual Ethernet port.

But, not all read-only memories are intended for use in microprocessor-based systems. Another vendor, Grammar Engine, has innovated the concept of emulating serial access read-onl,y memories which are commonly used as configuration ROMs for FPGAs.

Vendors

Applied Microsystems offers NetROM, a premium-quality ROM emulator. NetROM offers connectivity to your host system via ethernet for high-speed downloads. NetROM provides writeable memory for setting breakpoints in ROM space. And, you'll also find virtual UART support, as well as virtual Ethernet support.

NetROM supports a wide variety of debuggers from vendors including GreenHills, Integrated Systems, Inc., Microtec Research, Microware, Software Development Systems, and WindRiver. For more information on supported third-party products, you'll want to review Applied's Tool Guide.

Applied offers a variety of application notes on using NetROM with various debuggers and processors.

Grammar Engine Inc. (GEI) offers a broad range of products and features in their ROM emulators. GEI's products include: PromICE for basic ROM emulation, FlashICE for flash memory emulation, PromICE-Serial for FPGA configuration ROM emulation, and PromICE with Trace for giving in-circuit emulators a run for their money.

On the host side, GEI offers serial, parallel, or ethernet connectivity depending on your budget or your need for speed.

GEI's PromICE products support a long list of debuggers, including:

Incept Limited of Limerick, Ireland offers icePROM, a ROM emulator capable of fast 2-(MBps) downloads via your PC parallel port. Incept's icePROM also supports RAM emulation, allowing for target writes to the emulation space.

TechTools
Embedded Systems Development Tools

TechTools offers a full range of ROM emulators from the entry-level EconoROM II to the UniROM, which offers virtual UART support. The EconoROM II is a basic ROM emulator with parallel port for code downloads from your host system.

FlexROM II offers high-speed code download rates up to 2.5 MBps. It also offers a few ICE-like features, including hardware address matching (or hardware breakpoints) and read/write access from the target system.

To get a good close look at these products, manuals are available on-line for EconoROM II, FlexROM II, and UniROM.

An application note on communicating through the UniROM's Virtual UART is also available.

If you would like to add any information on this topic or request a
specific topic to be covered, contact Benjamin Day. Ben Day works for Schweitzer Engineering Laboratories in Pullman, Washington making electric power safer, more reliable, and more economical.

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