Altera CPRI IP Core - Manual (Page 78)

4–46 Chapter 4: Functional Description
CPU Interface
CPRI MegaCore Function December 2013 Altera Corporation
User Guide
Control Word Order
The entries in the control receive and control transmit tables match the organization of
control words in subchannels from the CPRI specification.
Figure 4–25 shows this
word order. The figure is Figure 15 of the CPRI V5.0 Specification.
Figure 4–25 illustrates how the 256 control words in the hyperframe are organized as
64 subchannels of four control words each. The figure illustrates why the index X of a
control word is Ns + 64 × Xs, where Ns is the subchannel index and Xs is the index of
the control word within the subchannel.
Control Word Transmission Example
To write to the vendor-specific portion of the control word in a transmitted
hyperframe, perform the following steps:
1. Identify the indices for the vendor-specific portion of the transmit control table,
using the formula X = Ns + 64 × Xs.
In the example, Ns = 16 and Xs = 0,1,2, and 3. Therefore, the indices to be written
are 16, 80, 144, and 208.
2. For each value X in 16, 80, 144, and 208, perform the sequence of steps listed in
“Writing the Outgoing Control Words” on page 4–44 .
Figure 4–25. Illustration of Subchannels in a Hyperframe
Xs == 0 1 2 3
Ns == 0 0: K28.5 Synchronization and Timing
1 1: HDLC link 65: HDLC 129: HDLC 193: HDLC
2 2: L1 In-band 66: L1 in-band 130: L1 in-band 194: P (20 = 0x14)
3 3: Reserved 67: Reserved
4 4: Ctrl_AxC ... ... ...
...
7 7: Ctrl_AxC 71: Ctrl_AxC 135: Ctrl_AxC 199: Ctrl_AxC
...
14 14: Reserved
15 15: Reserved 79: Reserved 143: Reserved 207: Reserved
16 Vendor-specific
...
19
20
Pointer P --->
20: Ethernet
...
62 62 126 190 254
63 63 127 191 255