HC4GX15 Datasheet, PDF (517/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 2: HardCopy IV GX Dynamic Reconfiguration
2–59
PMA Controls Reconfiguration
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 complete.
For example, if the number of channels controlled by the ALTGX_RECONFIG
instance is 2, the tx_vodctrl_out is 6 bits wide. The tx_vodctrl_out[2:0]
corresponds to channel 1 and similarly, tx_vodctrl_out[5:3] corresponds to
channel 2.
The following list shows the steps to read the V_OD values of the second channel:
1. Before you initiate a read transaction, set the rx_tx_duplex_sel[1:0] 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. Once 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. To read the current V_OD values in channel 2, observe the
values in tx_vodctrl_out[5:3].
© June 2009 Altera Corporation
HardCopy IV Device Handbook, Volume 3