Dell USA L P

Jeffrey W Porter

Anthony L Overfield

Disclosed is a circuit for assisting programmers in developing programs to be loaded into read-only memories within microprocessor-based systems. The circuit acts as a ROM emulator and is powered by the target computer system, thus removing the need for an external power supply. The circuit may be reprogrammed by the target computer system even if the target computer system is not designed to allow write cycles to read-only memory. The software to be developed is stored in an electrically erasable programmable read-only memory, and may be reprogrammed either from the target computer system or through the parallel interface of a host computer system.

System and method for ROM program development

A parallel port adapter, which provides a special buffering circuit on the four control lines from the system to the printer. This circuit provides a low-impedance bidirectional path for communication between the CPU and the printer, whenever any of the control lines is active. The circuit uses blocking diodes on all four lines, and uses pass transistors in parallel with the blocking diodes, and uses power-robbing to turn on the pass transistors whenever the port is in use.

Growing community of inventors

Austin, TX, United States of America

Jeffrey W Porter