DCLK-to-DATA[] Ratio (r) for FPP Configuration
Fast passive parallel (FPP) configuration requires a different DCLK-to-DATA[] ratio when you turn on encryption or the compression feature.
Depending on the DCLK-to-DATA[] ratio, the host must send a DCLK frequency that is r times the DATA[] rate in byte per second (Bps) or word per second (Wps). For example, in FPP ×16 where the r is 2, the DCLK frequency must be 2 times the DATA[] rate in Wps.
Cyclone® V devices use additional clock cycles to decrypt and decompress the configuration data. If the DCLK-to-DATA[] ratio is greater than 1, at the end of configuration, you can only stop the DCLK (DCLK-to-DATA[] ratio – 1) clock cycles after the last data is latched into the Cyclone® V device.
| Configuration Scheme | Encryption | Compression | DCLK-to-DATA[] Ratio (r) | 
|---|---|---|---|
| FPP (8-bit wide) | Off | Off | 1 | 
| On | Off | 1 | |
| Off | On | 2 | |
| On | On | 2 | |
| FPP (16-bit wide) | Off | Off | 1 | 
| On | Off | 2 | |
| Off | On | 4 | |
| On | On | 4 |