Altera Cyclone IV - Page 416

3–18 Chapter 3: Cyclone IV Dynamic Reconfiguration
Dynamic Reconfiguration Modes
Cyclone IV Device Handbook, November 2011 Altera Corporation
Volume 2
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
OD
values of the second channel, perform the
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
OD
values in channel 2, observe the values in
tx_vodctrl_out[5:3] .
In the waveform example shown in Figure 3–7, the transmit V
OD
settings written in
channels 1 and 2 prior to the read transaction are 3'b001 and 3'b010, respectively.
1 Simultaneous write and read transactions are not allowed.
Figure 3–7. Read Transaction Waveform—Use the same control signal for all the channels Option Enabled
Note to Figure 3–7:
(1) In this waveform example, you want to read from only the transmitter portion of all the channels.
read
busy
6'b111111 6'bXX XXX X 6'b010001
2'b00 2'b10(1)
reconfig_clk
data_valid
rx_tx_duplex_sel [1:0]
tx_vodctrl_out [2:0]