Altera Cyclone IV Device Handbook page 416

3–18
Read Transaction
If you want to read the existing values from a specific channel connected to the
ALTGX_RECONFIG instance, observe the corresponding byte positions of the PMA
control output port after the read transaction is completed.
For example, if the number of channels controlled by the ALTGX_RECONFIG is two,
the tx_vodctrl_out is 6 bits wide. The tx_vodctrl_out[2:0] signal corresponds to
channel 1 and the tx_vodctrl_out[5:3] signal corresponds to channel 2.
To complete a read transaction to the V
following steps:
1. Before you initiate a read transaction, set the rx_tx_duplex_sel port to 2'b10 so
that only the transmit PMA controls are read from the transceiver channel.
2. Ensure that the busy signal is low before you start a read transaction.
3. Assert the read signal for one reconfig_clk clock cycle. This initiates the read
transaction.
4. The busy output status signal is asserted high to indicate that the dynamic
reconfiguration controller is busy reading the PMA control settings.
5. When the read transaction has completed, the busy signal goes low. The
data_valid signal is asserted, indicating that the data available at the read control
signal is valid.
6. To read the current V
tx_vodctrl_out[5:3].
In the waveform example shown in
channels 1 and 2 prior to the read transaction are 3'b001 and 3'b010, respectively.
Figure 3–7. Read Transaction Waveform—Use the same control signal for all the channels Option Enabled
reconfig_clk
read
busy
data_valid
rx_tx_duplex_sel [1:0] (1)
tx_vodctrl_out [2:0]
Note to Figure 3–7:
(1) In this waveform example, you want to read from only the transmitter portion of all the channels.
1
Simultaneous write and read transactions are not allowed.
Cyclone IV Device Handbook,
Volume 2
values of the second channel, perform the
OD
values in channel 2, observe the values in
OD
Figure 3–7, the transmit V
2'b00
6'b111111
Chapter 3: Cyclone IV Dynamic Reconfiguration
Dynamic Reconfiguration Modes
settings written in
OD
2'b10
6'bXXXXXX 6'b010001
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