Achronix Speedster22i Configuration - Manual (Page 10)

10 UG033, December 18, 2013
In Figure 4 above:
1. After CONFIG_RSTN is deasserted, CPU_CLK needs to continue being clocked to
ensure that the FPGA cycles through the FCU states and the configuration memory is
cleared. At that point, CONFIG_STATUS is released and is pulled high.
2. Some time after CONFIG_STATUS is pulled high, CSN should be pulled low to
begin writing the bitstream data into the FPGA. When the last set of data is written
into the FPGA, CSN is pulled high.
3. Once CSN is pulled high, CPU_CLK needs to continue being clocked for a total of
about 12,000 clock cycles. After 9,000 clock cycles, CONFIG_DONE should be
asserted to indicate that configuration has completed, and the remaining 3,000 clock
cycles are needed to ensure that the FCU can successfully transition into user mode.
The waveform in Figure 5 depicts the window of a sample valid bitstream programming
section of the configuration.
CPU_CLK
CSN
DQ[7:0]
CONFIG_STATUS
AA 55 AA 55 20 20 16 41 00 00 00 00 00 00 00 00 00 38 00 01 00 00 00 07 11 15 00
Sync ID Code NOP NOP Write Cmd Write Data
Figure 5: Sample Valid Bitstream Programming
Serial x1 Flash
The Serial Flash programming mode allows flash memories to be used to configure the
Speedster22iHD FPGA. In this mode the FPGA is the master, and therefore supplies the clock
to the Flash memory.
Figure 6 below provides a block diagram of how a serial flash can be connected to a
Speedster22iHD FPGA in x1 mode.