Single step debug card using the PCI interface

摘要

This specification discloses a single step debug card using the PCI bus, which keeps the FRAME# of the PCI bus at a low voltage; latches and displays through an LED the address and command of the PCI bus cycle; keeps the control signal of read only memory and the IRDY# ready signal and TRDY# ready signal on the PCI bus at a low voltage, latches and displays through an LED the data and byte enable of the PCI bus cycle; outputs a device selection signal from a target device when the target device is detected; intercepts the PCI bus cycle when the device selection signal is kept at a low voltage and both the IRDY# ready signal and the TRDY# ready signal are kept at a low voltage; enables the PCI host to provide a retry function when the target device cannot respond a TRDY# ready signal before the PCI bus cycle ends so as to achieve the function of single step interruption debugging.