There are three distinct types of Conventional Reset and each of these causes the hardware state machines, hardware logic, port states and configuration registers to be initialized to their default values.
- Cold Reset – The reset occurring at power-up of the device is referred to as Cold Reset. Cold Reset is triggered by the PERSTn signal being asserted. PERSTn signal is an auxiliary signal in PCIе Specification and can be used at power on reset for the device that has PCIe as its primary bus interface to rest of the system. The device is allowed to generate its own power-on reset as long as the PCIe requirements for PERSTn are met. See PCIe Base Specifications for details.
- Warm Reset – A reset can be triggered by the hardware without the removal of power from the device. This reset is referred to as Warm Reset. The hardware implementation is not specified by the PCIе Specification.
- Hot Reset – The PCIе Specifications provides an in-band mechanism to propagate a Conventional Reset across a Link. This reset, called the Hot Reset, propagates via the transmission of TS1 Ordered Sets. In general, Hot Reset is software controlled procedure and can only be issued by Root Port in a PCIе network as the propagation is downstream only. PCIe subsystem translates the received in-band hot reset into an interrupt that can then be used by software to reset the PCIe subsystem.
After a conventional reset, the software must wait at least 100 ms before attempting any PCIe transaction on the device that has been reset. If the downstream device does not respond to transaction packets, it must not give up until 1 second plus an additional 50% (0.5 second) time is lapsed.