The LPD-Q supports from 1-8 device Q-Channel interfaces and can be configured to operate in the following modes:

Q-Channel expander

The controller Q-Channel transition request is broadcast to all device Q-Channels, in parallel. The transition requests that are sent to the devices can complete in any order.

Q-Channel sequencer

A controller Q-Channel transition request is passed sequentially to each device Q-Channel. Each transition request must complete before the LPD-Q can send a transition request to the next device.

The control Q-Channel (ctrl_* signals) receives power mode requests from the Q-Channel controller. The LPD-Q uses the device Q-Channels (dev_* signals) to send the requests to the devices. The LPD-Q uses clk_qactive_o to indicate when it requires a clock signal, clk.

The ctrl_qactive_o output is the logical OR of the multiple device inputs, dev_qactive_i<X>. The path from the dev_qactive_i<X> signals to the ctrl_qactive_o output is a combinatorial path.

The clk_qactive_o is a Q-Channel signal that is HIGH:

• When a device has the dev_qreqn_o<X> and dev_qacceptn_i<X> signals in opposites states.
• When any dev_qdeny_i<X> is HIGH.
• When ctrl_qreqn_i and ctrl_qacceptn_o signals are in opposites states.
• When ctrl_qdeny_o is HIGH.

The type of response that the LPD-Q generates to the controller, in response to a quiescence request, depends on the responses that the LPD-Q receives from the devices:

• The LPD-Q accepts a controller quiescence request, if all devices indicate acceptance of the quiescence request by setting dev_qacceptn_i<X> LOW. When all the dev_qacceptn_i<X> are LOW, then the LPD-Q sets ctrl_qacceptn_o LOW.

• The LPD-Q denies a controller quiescence request, either when:

  • A dev_qdeny_i<X> asserts, in response to the assertion of dev_qreqn_o<X>.
  • A dev_qactive_i<X> goes HIGH, between the assertion of all dev_qreqn_o<X> signals and the assertion of the last dev_qacceptn_i<X>. This behavior only occurs when the ACTIVE_DENY configuration parameter is set to 1.

  When either of these denial conditions occur, then the LPD-Q sets ctrl_qdeny_o HIGH.