Live system upgrade

A network element, comprising:

• a PLD (programmable logic device) having a configuration memory therein;
• a nonvolatile memory;
• one or more circuits controlled at least in part by system control signals to handle network traffic;
• a signal control device, external to the PLD, the signal control device comprising:
• a plurality of resistors attached to output or I/O pins of the PLD and driven by at least one signal line controlled by the processor or state machine;
• and
• a processor or state machine, configured to write PLD configuration data to the nonvolatile memory, direct the signal control device to hold the system control signals at a predefined state, load the PLD configuration data from the nonvolatile memory into the configuration memory while the signal control device holds the system control signals at the predefined state, and, responsive to completion of the loading of the configuration memory, direct the signal control device so that operation of the system control signals is in accordance with direction by the PLD.

A tangible, non-transitory, computer-readable media having instructions thereupon which, when executed by a processor in a network element, cause the processor to perform a method comprising:

• writing PLD (programmable logic device) configuration data to a nonvolatile memory in the network element, so that a PLD in the network element can be reconfigured;
• directing a signal control device that is internal to the network element, external to the PLD, and coupled to system control signals, to hold the system control signals at a predefined state, the directing the signal control device to hold the system control signals at the predefined state comprises:
• driving one or more control lines, attached to a plurality of resistors that are attached to signal lines having the system control signals, to a first state, with PLD outputs or I/Os (input/outputs) in a high impedance state and attached to the signal lines;
• loading the PLD configuration data from the nonvolatile memory into a configuration memory while the signal control device holds the system control signals at the predefined state;
• and
• directing the signal control device to cease holding the system control signals at the predefined state and allow the system control signals to be operated by the PLD, responsive to completion of the loading into the configuration memory.