Critical Issue
The description of the cpri_rx_cnt_sync port
(bits [4:2] of the extended_rx_status_data bus) in
the
CPRI MegaCore Function User Guide is incorrect for CPRI MegaCore
function versions 10.0 and 10.1. The description in the Extended
Rx Status Signals table in Chapter 5, Signals incorrectly describes
the port, and the description of the initialization sequence for
the testbenches, in Chapter 7, Testbenches, incorrectly implies
this port has value 0x2 when frame synchronization completes.
In addition, Figure 4-10 in Chapter 4, Functional Description is mislabeled. The state labeled XSYNC3 should instead be labeled HFNSYNC1, and the state labeled HFNSYNC should instead be labeled HFNSYNC2.
The correct description of this port tells you that the port
indicates the current state number (starting from zero rather than
one) among the states whose category is indicated by the cpri_rx_state port
(bits [1:0] of the extended_rx_status_data bus). For
example, if the value of cpri_rx_state is 2’b10, the
frame synchronization machine is in an XSYNC state. The cpri_rx_cnt_sync port
tells you which XSYNC state the machine is in: if cpri_rx_cnt_sync has
value 2’b00, the machine is in the state XSYNC1, and if it has value
2’b01, the machine is in state XSYNC2. Refer to the frame synchronization
state machine figure in Chapter 4, Functional Description, with
the modifications described in this erratum.
Therefore, when cpri_rx_state has value 2’b11, cpri_rx_cnt_sync cannot
have value 0x2. The frame synchronization machine has only two HFNSYNC
states. After frame synchronization completes, the value of cpri_rx_cnt_sync is
3b’001, not 3b’010 as erroneously indicated in the Testbenches chapter.
If you interpret the cpri_rx_cnt_sync port according
to the description in the user guide, you wait for a value that
will never appear to signal the HFNSYNC state of the CPRI frame
synchronization machine.
Interpret the cpri_rx_cnt_sync port (bits [4:2]
of the extended_rx_status_data bus) according to this
erratum rather than according to the description in the Signals chapter
of the CPRI MegaCore Function User Guide.
This issue is fixed in version 11.0 of the CPRI MegaCore Function User Guide.