Altera CPRI IP Core - Manual (Page 159)

Appendix B: Implementing CPRI Link Autorate Negotiation B–3
Configuring the CPRI IP Core for Autorate Negotiation
December 2013 Altera Corporation CPRI MegaCore Function
User Guide
Configuring the CPRI IP Core for Autorate Negotiation
To ensure that the CPRI IP core implements autorate negotiation correctly, while
configuring your CPRI IP core, enable autorate negotiation and set the CPRI line rate
to the maximum line rate the device family supports.
Running Autorate Negotiation
After your CPRI IP core is configured on the device, the autorate negotiation logic you
configured in your design outside the CPRI IP core must perform certain steps to
activate the autorate negotiation support logic in the CPRI IP core. This section
describes these steps.
To start autorate negotiation in your CPRI IP core, in addition to its own initialization
outside the CPRI IP core, your hardware and software must perform the following
steps:
1. Confirm that the i_datarate_en bit of the AUTO_RATE_CONFIG register is set to 1.
The AUTO_RATE_CONFIG register is described in Table 7–21 on page 7–11 . You can
read this value on the datarate_en output signal.
Figure B–2. Autorate Negotiation in Master Clocking Mode
Notes for Figure B–2 :
(1) Optional clock switching logic determines the value of gxb_refclk , depending on the desired transceiver frequency setting.
(2) The number of ROMs and the rate requirements are design dependent.
CPRI MegaCore Function
gxb_refclk
AUTORATE_CONFIG
Register
ALTGX
pll_inclk
122.88 MHz
153.6 MHz
61.44 MHz
30.72 MHz
76.8 MHz GPLL
Line Rate
Software controls
line rate based on
frame synchronization
FSM feedback.
15.36 MHz
(1)
ALTGX_RECONFIG
or
Altera Transceiver
Reconfiguration Controller
(2)
ROM
3072.0 Mbps
MIF file in
ROM
4915.2 Mbps
MIF file in
ROM
6144.0 Mbps
MIF file in
ROM
2457.6 Mbps
MIF file in
ROM
1228.8 Mbps
MIF file in
ROM
614.4 Mbps
MIF file in
ALTPLL_RECONFIG
(for Cyclone IV GX
devices)
(2)
ROM
1228.8 Mbps
MIF file in
ROM
2457.6 Mbps
MIF file in
ROM
3072.0 Mbps
MIF file in
ROM
614.4 Mbps
MIF file in
datarate_en
datarate_set
To MPLL
in Cyclone IV GX
devices
reconfig_fromgxb or
reconfig_from_xcvr,
reconfig_togxb or
reconfig_to_xcvr