Principle of PCI bus (III)

PCI that is, Peripheral Component Interconnect , Chinese meaning" peripheral device interconnection ", by pcisig (pCI Special Interest Group) A local parallel bus standard. Currently, electronic devices are widely used. The following describes PCI the working principle of the bus is helpful to everyone.

PCI typical bus connection method

for the typical connection method of the PCI bus, click to see the figure clearly.

 

PCIBusIdselPin Handling Method

Master PCI Bridge slice Idsel The pin is generally pulled to the ground through a resistor PCI Device Idsel Pin and AD [11: 31] Connected, each PCI Connect one of the two devices. As shown in.

 

PCISignal Driving Method

PCI the signal is a half-wave driving method. To better illustrate what a half-wave driving method is, I will use a simulation instance to describe it. It is a simulation link.

 

Shows the simulated waveform. ()

 

 

As you can see, Pci_out_3.3v The output is first about 2.3 v To drive the bus. 2ns After the delay, the signal arrives at the receiving end, and the receiver impedance does not match. The signal is reflected back to the start end, And the reflected signal passes through 2ns After the delay arrives at the start end, the driving signal and the reflection signal are superimposed on the start end. Pci_out_3.3v At about 4ns To reach the full range. 3.3 V . After a short period of oscillation, the system tends to be balanced. Because most PCI The limited-width device is built in the device chip, so PCI Serial matching resistance can be added for signals not at the start. PCI The signal is fast and stable. Only when the string resistance is added, the signal amplitude is lower PCI The service life of the device is longer.