Installation
PSM-500/500L/500LT SCPC Satellite Modem
Page 2-26
PSM-500/500L/500L T- Rev. 0.91
provides additional front panel and remote control parameter settings allowing control of the
option.
The modem’s two FEC slots are identical, and if similar functions exist on two cards the modem
will select a requested FEC option from the first slot which has that capability
In some cases when options are first introduced a software update to the modems internal
program is necessary to allow use of the option. Refer to Section 4.3 “
Updating Modem
Software
”. The Datum Systems’ M500 Update program will also recognize and install software for
FEC cards present in the modem.
The physical arrangement of the two FEC slots is shown in Figure 2-x below. The same PWB is
used for the standard Viterbi, Trellis Code Modulation and Reed-Solomon FECs with the
manufacturing option to add either the TPC4k or TPC16k chips when ordered. If these options
are ordered later a new board is supplied that has all of the necessary FEC capabilities and the
original standard FEC may be removed.
FlexLDPC
has a unique PWB, but comes standard with
Viterbi, Trellis Code Modulation and Reed-Solomon FECs, and is configurable to add either the
TPC4k or TPC16k chips when ordered.
2.11.1 Turbo Product Codes Option Installation
The PSM-500 Modem contains on-board circuitry and connectors for adding a Turbo Product
Codes Option Card. This card can co-exist with the IBS Multiplexer (and the Reed-Solomon
function also, but both cannot be used simultaneously).
Turbo Product Codes or TPC is available in multiple mechanical forms and also versions
depending on the link requirements. The three versions are a TPC4K which uses the same TPC
chip as in the PSM-4900 series of modems, and a TPC16K which uses a newer 16K block size to
improve performance, and a TPC-20K board with both the TPC4k and TPC16k chips installed.
Because of the larger processed block size, the TPC16K device has much higher delay or
latency than the 4K block device. It is also more expensive.
The modem can be ordered with any of these TPC options from the factory, and will then
normally be supplied as added components on the standard FEC card already containing the
Viterbi, TCM and Reed-Solomon FECs. Only one of these four versions can be installed on the
standard FEC card, and the type cannot be changed.
The other possibility is to add a card which has one of these two TPC chips into the Slot B of a
modem which already has Slot A occupied by the standard FEC card. Installation of these cards
is into a common SO-DIMM, 144 pin socket, and should be installed only by a qualified
technician.
The modem automatically recognizes the presence of the option card(s) and capabilities and
provides additional front panel and remote control parameter settings to control the option.
The Turbo Product Codes option, when enabled, replaces the convolutional encoder/Viterbi
decoder functions. The Modulator (Transmit) and Demodulator (Receive) functions of each option
are also independent and can be enabled and disabled as required.
Top and side views of the FEC cards are shown in Figure 2-5 below. For additional information
on the installation and configuration of the Turbo Product Codes option refer to Appendix TPC.
