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8–4
Chapter 8: Low Latency PHY IP Core
Parameter Settings
Altera Transceiver PHY IP Core
March 2012
Altera Corporation
User Guide
Table 8–4
lists
Standard
and
10G
datapath widths for the FPGA fabric-transceiver
interface, the PCS-PMA interface, and the resulting frequencies for the
tx_clkout
and
rx_clkout
parallel clocks. In almost all cases, the parallel clock frequency is described
by the following equation:
frequency
parallel clock
= data rate/FPGA fabric-transceiver interface width
1
The FPGA fabric-transceiver interface width is always 128 bits for the
GT
datapath.
FPGA fab
r
ic
tr
ansceive
r
in
t
e
r
face wid
t
h
8
,
10
,
16
,
20
,
32
,
40, 50, 64, 66, 128
This option indicates the parallel data fabric transceiver interface
width. GT datapath supports a single width of 128 bits. Refer
to
Table 8–4
for the supported interface widths of the
S
t
anda
r
d
and
10G
datapaths.
PCS-PMA in
t
e
r
face wid
t
h
8, 10, 16, 20, 32,
30, 64
The
PCS-PMA in
t
e
r
face wid
t
h
depends on the F
PGA fab
r
ic
tr
ansceive
r
in
t
e
r
face wid
t
h
and the Datapath type. Refer to
Table 8–4
for the supported interface widths of the
S
t
anda
r
d
and
10G
datapaths.
PLL
t
ype
CMU
ATX
The
CMU
PLL is available for the
S
t
anda
r
d
and
10G
datapaths.
The
ATX
PLL. is available for the
S
t
anda
r
d
,
10G
, and
GT
datapaths. The
CMU
PLL has a larger frequency range than the
ATX
PLL. The
ATX
PLL is designed to improve jitter performance
and achieves lower channel-to-channel skew; however, it
supports a narrower range of data rates and reference clock
frequencies. Another advantage of the
ATX
PLL is that it does not
use a transceiver channel, while the
CMU
PLL does.
An informational message displays in the message panel if the
PLL
t
ype
that you select is not available at the frequency
specified.
Da
t
a
r
a
t
e
S
t
anda
r
d:
1–8.5 Gbps
10G:
1–12.5 Gbps
GT:
20–28 Gbps
Specifies the data rate in Mbps.
Base da
t
a
r
a
t
e
1 ×
Lane
r
a
t
e
2 ×
Lane
r
a
t
e
4 ×
Lane
r
a
t
e
Select a
base da
t
a
r
a
t
e
that minimizes the number of PLLs
required to generate all the clocks required for data transmission.
By selecting an appropriate
base da
t
a
r
a
t
e
, you can change data
rates by changing the divider used by the clock generation block.
For higher frequency data rates 2 × and 4× base data rates are not
available.
Inpu
t
clock f
r
equency
Variable
Specifies the frequency of the PLL input reference clock. The
frequency required is the
Base da
t
a
r
a
t
e
/2. You can use any
Inpu
t
clock f
r
equency
that allows the PLLs to generate this
frequency.
Table 8–3. General Options
Name Value
Description
Table 8–4. Datapath Width Support (Part 1 of 2)
FPGA Fabric-Transceiver
Interface Width
PCS-PMA Interface Width
tx_clkout and rx_clkout
frequency
Standard Datapath
10G Datapath
8
8
—
data rate/8
10
10
—
data rate/10