
Appendix E: Delay Measurement and Calibration E–25
Single-Hop Delay Measurement
December 2013 Altera Corporation CPRI MegaCore Function
User Guide
Round-Trip and Cable Delay Calculation Example 4: Two Different Device
Families
This example describes the calculation for the case of two link partner CPRI IP cores
configured with autorate negotiation enabled in a single-hop configuration, running
at CPRI data rate 3.072 Gbps. The REC master is configured on an Arria II GX device
and the RE slave is configured on a Stratix IV GX device.
The calculation is identical to the calculation in Example 3, except that the register
values vary, and different table columns are relevant in Table E–1, Table E–3,
Table E–6, and Table E–7.
Table E–10. Example 3 Data and Calculations
Calculation
Component
Delay Component Relevant Register Value or Source Table Delay
Total
(decimal)
Round trip delay
rx_round_trip_delay
= 0x69 105
REC Tx path delay
T_T4 Table E–6 on page E–14 7
18.10
Tx buffer delay
tx_ex_buf_delay
= 0x3B9 7.50
T_txv_TX
tx_bitslipboundaryselect
= 0x0
Table E–7 on page E–16
3.6
REC Rx path delay
T_txv_RX
rx_bitslipboundaryselectout
= 0x8
Table E–1 on page E–5
7
47.25
Rx buffer delay
rx_ex_buf_delay
= 0x1000 32.25
Calibration pointer
cal_pointer
= 3 3
Byte alignment
rx_byte_delay
= 0 0
T_R1 Table E–3 on page E–8 5
T14 (Round trip delay minus REC Tx path delay minus REC Rx path delay) 39.65
RE Tx path delay
T_T4 Table E–6 on page E–14 6.5
18.585
Tx buffer delay
tx_ex_buf_delay
= 0x46B 8.91
T_txv_TX
tx_bitslipboundaryselect
= 0x3
Table E–7 on page E–16
3.175
RE Rx path delay
T_txv_RX
rx_bitslipboundaryselectout
= 0x5
Table E–1 on page E–5
5.575
19.475
Rx buffer delay
rx_ex_buf_delay
= 0x2ED 5.90
Calibration pointer
cal_pointer
= 3 3
Byte alignment
rx_byte_delay
= 0 0
T_R1 Table E–3 on page E–8 5
Loopback delay on RE slave 1
Toffset (RE Tx path delay + RE Rx path delay + loopback delay) 39.06
Cable delay (T14 minus Toffset) 0.59
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