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Chapter 11: Deterministic Latency PHY IP Core 11–5
Delay Estimation Logic
November 2012 Altera Corporation Altera Transceiver PHY IP Core
User Guide
Delay Estimation Logic
This section provides the equations to calculate delays when the Deterministic
Latency PHY IP Core implements CPRI protocol. CPRI defines the radio base station
interface between network radio equipment controllers (REC) and radio equipment
(RE) components.
For RE
RX_latency_RE = <RX PCS latency in parallel clock cycles>
+
(<RX PMA latency in UI>
+ <PMA uncertainty reported by wordalignment_boundary[5]>)
TX_latency_RE = <TX PCS latency in parallel clock cycles>
+ <TX PMA latency in UI >

Tx bitslip latency>
For REC
RX_latency_REC = <RX PCS latency in parallel clock cycles>
+ <RX PMA latency in UI> + < rx_clkout phase shift of tx_clkout>
TX_latency_REC = <TX PCS latency in parallel clock cycles>
+ <TX PMA latency in UI>
Round Trip Delay
Launch_time (from TX pins) =<clock arrival time> + <data arrival time>
= <clock arrival time>
+ <TX latency in REC> (tx bitslip=0)
= <t
PD
GPLL to CMU PLL - t
feedback
>
+ ((<TX_latency in REC> × <tx_clkout_period>)
+ t
TX_tclock_output
)
Arrival_time (at RX pins) = <latency time in RE> - <RX latency time in REC>
= (<Round_trip_latency> × <tx_clkout_period>)
– ((<RX_latency in REC> × <rx_clkout_period>)
+ <t
PDIO>RX_deser
>
+ <rx_clkout_phase_WRT_tx_clkout/360 × rx_clkout_period>)
Total Delay = <Arrival_time><Launch_time>
Total Delay Uncertainty
Round trip delay estimates are subject to process, voltage, and temperature (PVT)
variation.
t
RXCLK_Phase_detector_uncertainty
= 2 × max(<t
GLL_phase_step
>, <t
CDR_to_GPLL_jitter
>) + µt
SU
+ µt
H
t
Round_trip_uncertainty
= <t
RX_CLK_Phase_detector_uncertainty
+ t
GPLL->CMU PLL_variation
>
+<t
feedback_variation
> + <t
TX_tco_variation
> + <t
IO->RXdeser_delay_variation
>
+ <t
PLL_multicycle_jitter
> + <t
offset_uncertainty
>
Seitenansicht 218
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