1–10
Chapter 1: Cyclone IV Transceivers Architecture
Transmitter Channel Datapath
February 2015
Altera Corporation
Transmitter Output Buffer
shows the transmitter output buffer block diagram.
The Cyclone IV GX transmitter output buffers support the
1.5-V PCML
I/O standard
and are powered by
VCCH_GXB
power pins with 2.5-V supply. The 2.5-V supply on
VCCH_GXB
pins are regulated internally to 1.5-V for the transmitter output buffers. The
transmitter output buffers support the following additional features:
■
Programmable differential output voltage (V
OD
)—customizes the V
OD
up to
1200 mV to handle different trace lengths, various backplanes, and various
receiver requirements.
■
Programmable pre-emphasis—boosts high-frequency components in the
transmitted signal to maximize the data eye opening at the far-end. The
high-frequency components might be attenuated in the transmission media due to
data-dependent jitter and intersymbol interference (ISI) effects. The requirement
for pre-emphasis increases as the data rates through legacy backplanes increase.
■
Programmable differential on-chip termination (OCT)—provides calibrated OCT
at differential 100
or 150
with on-chip transmitter common mode voltage
(V
CM
) at 0.65 V. V
CM
is tri-stated when you disable the OCT to use external
termination.
1
Disable OCT to use external termination if the link requires a 85
termination, such
as when you are interfacing with certain PCIe Gen1 or Gen2 capable devices.
f
The Cyclone IV GX transmitter output buffers are current-mode drivers. The resulting
V
OD
voltage is therefore a function of the transmitter termination value. For lists of
supported V
OD
.
Figure 1–11. Transmitter Output Buffer Block Diagram
Note to
:
(1) Receiver detect function is specific for PCIe protocol implementation only. For more information, refer to
Express (PIPE) Mode” on page 1–52
GXB_TXp
GXB_TXn
Programmable
Pre-emphasis
and V
OD
Receiver
Detect
(1)
50
or 75
50
or 75
+ V
CM
-
Содержание Cyclone IV
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