Altera CPRI IP Core - Manual (Page 75)

Chapter 4: Functional Description 4–43
CPU Interface
December 2013 Altera Corporation CPRI MegaCore Function
User Guide
Table 4–13 summarizes the relevant register fields. For complete information, refer to
the register tables in Chapter 7, Software Interface .
Recording and Retrieving the Incoming Control Words
A control receive table contains one entry for each of the 256 control words in the
current hyperframe. To read a control word, your application must write the control
word number X to the
cpri_ctrl_index field of the CPRI_CTRL_INDEX register and
then read the last received #Z.X control word from the CPRI_RX_CTRL register. Because
the register can hold only 32 bits at a time, depending on the CPRI line rate, reading
the full control word may require multiple register accesses. Increment the value in
the
cpri_ctrl_position field of the CPRI_CTRL_INDEX register from zero to three to
Table 4–13. Register Support for Control Word Access
Register
Register
Bits
Field Name Description
CPRI_CTRL_INDEX
( Table 7–7 )
[16] tx_control_insert
Control word 32-bit section transmit enable. This value is stored
in the control transmit table with its associated entry. When you
change the value of the
cpri_ctrl_index field, the stored
tx_control_insert value associated with the indexed entry
appears in the tx_control_insert field.
At the time the CPRI IP core can insert a control transmit table
entry in the associated position in the outgoing hyperframe on
the CPRI link, if the
tx_control_insert bit associated with
that entry has the value of 1, and the tx_ctrl_insert_en bit
of the CPRI_CONFIG register is asserted, the IP core inserts the
table entry in the hyperframe.
[9:8] cpri_ctrl_position
Sequence number for CPRI control word 32-bit section
monitoring and insertion. The value in this field determines the
32-bit section of the control receive and control transmit table
entries that appear in the
CPRI_RX_CTRL and CPRI_TX_CTRL
registers.
[7:0] cpri_ctrl_index
Index for CPRI control word monitoring and insertion. The value
in this field determines the control receive and control transmit
table entries that appear in the
CPRI_RX_CTRL and
CPRI_TX_CTRL registers.
CPRI_RX_CTRL
( Table 7–8 )
[31:0] rx_control_data
Most recent received CPRI control word 32-bit section from
CPRI hyperframe position Z.x, where x is the index in the
cpri_ctrl_index field of the CPRI_CTRL_INDEX register. The
cpri_ctrl_position field of the CPRI_CTRL_INDEX register
indicates whether this is the first, second, third, or fourth such
32-bit section.
CPRI_TX_CTRL
( Table 7–9 )
[31:0] tx_control_data
32-bit section of CPRI control word to be transmitted in CPRI
hyperframe position Z.x, where x is the index in the
cpri_ctrl_index field of the CPRI_CTRL_INDEX register. The
cpri_ctrl_position field of the CPRI_CTRL_INDEX register
indicates whether this is the first, second, third, or fourth such
32-bit section.
CPRI_CONFIG
( Table 7–6 )
[0] tx_ctrl_insert_en
Master enable for insertion of control transmit table entries in
CPRI hyperframe. This signal enables control words for which
the
tx_control_insert bit is high to be written to the CPRI
frame.