Chapter 6: PHY IP Core for PCI Express (PIPE)
6–3
Parameter Settings
March 2012
Altera Corporation
Altera Transceiver PHY IP Core
User Guide
Analog Options
You specify the analog parameters for Stratix V devices using the Quartus II
Assignment Editor, the Pin Planner, or through the Quartus II Settings File (
.qsf
). The
default values for analog options fall into three categories:
■
Global
— These parameters have default values that are independent of other
parameter settings.
■
Computed
—These parameters have an initial default value that is recomputed
based on other parameter settings.
■
Proxy
—These parameters have default values that are place holders. The
Quartus II software selects these initial default values based on your design;
however, Altera recommends that you replace these defaults with values that
match your electrical board specification.
PLL
t
ype
CMU
ATX
You can select either the CMU or ATX PLL. 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. For example, if a
base da
t
a
r
a
t
e
of
2500 Mbps
is not available with the
ATX
PLL and a
100 MHz
reference
clock; however,
base da
t
a
r
a
t
es
of
5000 Mbps
or
10000 Mbps
are
possible with the
ATX
PLL and
100 MHz
reference clock. Another
advantage of the ATX PLL is that it does not use a transceiver channel,
while the CMU PLL does.
PLL
r
efe
r
ence clock
f
r
equency
100 MHz
125 MHz
If you specify a CMU PLL for the TX PLL, you can use either the
100 MHz
or
125 MHz
input reference clock.
Dese
r
ializa
t
ion fac
t
o
r
8, 16
Specifies the width of the interface between the PHYMAC and PHY
(PIPE). Using the 16-bit interface, reduces the required clock
frequency by half at the expense of extra FPGA resources.
PIPE low la
t
ency
synch
r
onous mode
On/Off
When enabled, the rate match FIFO is in low latency mode.
Run leng
t
h 5–160
Specifies the legal number of consecutive 0s or 1s.
Enable elec
tr
ical idle
infe
r
encing
T
r
ue/False
When
T
r
ue
, enables the PIPE interface to infer electrical idle instead of
detecting electrical idle using analog circuitry. For more information
about inferring electrical idle, refer to
“
S
ection 4.2.3.4 Inferring
Electrical Idle”
in the
PCI Express Base Specification 2.0.
Table 6–3. General Options (Part 2 of 2)
Name
Value
Description