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LatticeECP2/M sysCONFIG Usage Guide
• The bitstream can be compressed
• The Persistent option can be set
• Configuration pins can be protected
• DONE pin options can be selected
By setting the proper parameter in the Lattice design software the selected configuration options are set in the gen-
erated bitstream. As the bitstream is loaded into the device the selected configuration options take effect. These
options are described in the following sections.
Bypass Option
In ispLEVER, the Bypass option can be set by using the Bitgen properties. Or, a chain of bitstreams can be assem-
bled and Bypass set using ispVM. To set the Bypass option in Diamond, see Appendix A. The Bypass option can
be used in parallel and serial mode daisy chains. The Bypass option is not supported when using SPIm configura-
tion. The Bypass option is not supported when using encrypted bitstream files with the LatticeECP2/M S-Series
devices. Please refer to TN1109,
LatticeECP2/M Configuration Encryption Usage Guide
, for more information
about using encrypted bitstream files.
When the first device completes configuration, and a Bypass command is input from the bitstream, any additional
data coming into the FPGA configuration port will overflow serially on DOUT. This data is applied to the DI pin of
the next device (downstream devices must be set to slave serial mode).
In serial configuration mode the Bypass option connects DI to DOUT via a bypass register. The bypass register is
initialized with a ‘1’ at the beginning of configuration and will stay at that value until the Bypass command is exe-
cuted. In parallel configuration mode the Bypass option causes the excess data coming in on D[0:7] to be serially
shifted to DOUT. The serialized data is shifted to DOUT through a bypass register. D0 will be shifted out first fol-
lowed by D1, D2, and so on. Once the Bypass option starts the device will remain in Bypass until the Wake-up
sequence completes. In parallel mode, if Bypass needs to be aborted, drive both CSN and CS1N high, this acts as
a Bypass reset signal.
Flowthough Option
As with Bypass, Flowthrough can be set in the Bitgen properties in ispLEVER and in the Strategy Process Options
settings. To set the Flowthrough option in Diamond, see Appendix A. The Flowthrough option can be used with par-
allel daisy chains only. The Flowthrough option is not supported when using SPIm configuration. The Flowthrough
option not supported when using encrypted bitstream files with the LatticeECP2/M S-Series devices. Please refer
to TN1109,
LatticeECP2/M Configuration Encryption Usage Guide
, for more information about using encrypted bit-
stream files.
When the first device completes configuration, and a Flowthrough command is input from the bitstream, the CSON
pin is driven low. In addition to driving CSON low, Flowthrough also tri-states the device’s D[0:7] and BUSY pins in
order to avoid contention with the other daisy-chained devices. Once the Flowthrough option starts the device will
remain in Flowthrough until the Wake-up sequence completes. If Flowthrough needs to be aborted drive both CSN
and CS1N high, this acts as a Flowthrough reset signal.
Master Clock
If the CFG pins indicate an SPI or SPIm mode the CCLK pin will become an output, with the frequency set by the
user. The default Master Clock Frequency is 3.1 MHz. For a complete list of the supported Master Clock frequen-
cies, please see the
LatticeECP2/M Family Data Sheet
. When using the LatticeECP2/M S-Series devices, the
available frequencies are restricted, as shown in the data sheet.
The user can change the Master Clock frequency by setting the MCCLK_FREQ global preference in the Lattice
ispLEVER Design Planner. To set this option in Diamond, see Appendix A. One of the first things loaded during
configuration is the MCCLK_FREQ parameter; once this parameter is loaded the frequency changes to the
selected value using a glitchless switch. Care should be exercised not to exceed the frequency specification of the
slave devices or the signal integrity capabilities of the PCB layout.
