2–156
Altera Corporation
Stratix II GX Device Handbook, Volume 2
October 2007
Native Modes
The
powerdn
port transitions the transceiver into different power states.
The encoded value is shown in
Table 2–34
. The
pipephydonestatus
signal reacts to the
powerdn
request and pulses high for one parallel
clock cycle.
There are specific functions that are performed at each of the power
states. The power-down states are for PIPE emulation. The transceiver
does not go into actual power saving mode, with the exception of the
transmitter buffer for Electrical Idle. This shouldn’t matter because the
power consumption for the PLD logic is much greater than the
transceiver power consumption. Powering down the transceiver does not
save much when compared to the overall power consumption of the
entire device.
Table 2–34
shows each power state and its function.
There are two signals associated with the power states:
tx_detectrxloopback
and
tx_forceelecidle
. The
tx_detectrxloopback
signal controls whether the channel goes into
loopback when the power state is in P0 or receiver detect when in P1 state.
This signal does not have any affect in any other power states. The
tx_forceelecidle
signal governs when the transmitter goes into an
Electrical Idle state. The
tx_forceelecidle
signal is asserted in P0s
and P1 states and deasserted in P0 state. In P2 state, under normal
conditions, the
tx_forceelecidle
signal is asserted and then
deasserted when the beacon signal must be sent out, signifying the intent
to exit the P2 power-down state.
Table 2–35
shows the behavior of the
tx_detectrxloopback
and
tx_forceelecidle
signals in the power
states.
Table 2–34. Power State Functions and Descriptions
Power State
powerdn
Function
Description
P0
2’b00
Transmits normal data,
transmits Electrical Idle,
or enters into loopback
mode.
Normal operation mode
P0s
2’b01
Only transmits Electrical
Idle.
Low recovery time power
saving state
P1
2’b10
Transmitter buffer is
powered down and can
do a receiver detect while
in this state.
High recovery time power
saving state
P2
2’b11
Transmits Electrical Idle
or a beacon to wake up
the downstream receiver.
Lowest power saving
state
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