HC4GX15 Datasheet, PDF (319/668 Pages) Altera Corporation – HardCopy IV Device Handbook

Chapter 1: HardCopy IV GX Transceiver Architecture
1–55
Transmitter Channel Datapath
pre-emphasis on the data bit before the transition. The 1st post-tap and 2nd post-tap
sets the pre-emphasis on the transition bit and the successive bit, respectively. The
pre-tap and 2nd post-tap also provide inversion control, shown by negative values on
the corresponding tap settings in the ALTGX MegaWizard Plug-In Manager. The
ALTGX MegaWizard Plug-In Manager only shows the valid pre-emphasis tap values
for a selected V_OD and transmitter termination resistance setting.
Programmable Transmitter Output Buffer Power (VCCH)
The ALTGX MegaWizard Plug-In Manager provides an option to select V_CCH.
1 Two options are available for V_CCH: 1.4 V or 1.5 V. With 1.4 V, the data rate range is
600 Mbps to 6.5 Gbps; with 1.5 V, the data rate range is 600 Mbps to 4.25 Gbps.
Common Mode Voltage (VCM) Settings
HardCopy IV GX devices provide a VCM of 650 mV.
Link Coupling
A high-speed serial link can be AC-coupled or DC-coupled, depending on the serial
protocol being implemented.
AC-Coupled Links
In an AC-coupled link, the AC-coupling capacitor blocks the transmitter DC common
mode voltage. The on-chip or off-chip receiver termination and biasing circuitry
automatically restores the selected common mode voltage. Figure 1–43 shows an
AC-coupled link.
Figure 1–43. AC-Coupled Link
Transmitter
AC Coupling
Capacitor
Physical Medium
Receiver
TX Termination
Physical Medium
AC Coupling
Capacitor
RX Termination
TX
RX
V_CM
V_CM
© June 2009 Altera Corporation
HardCopy IV Device Handbook Volume 3