How to start SPI reconfiguration of Spartan 6 via JTAG
I am going to use SPI FLASH for configuration of Spartan 6 (Master SPI mode). The SPI FLASH will be directly programmed in system. After the FLASH is programmed Spartan 6 must be forced to load a new configuration from the FLASH. I know it can be done by pulling PROGRAM_B low. But is it possible to issue reconfiguration using JTAG interface?
You can trigger a re-programming of the FPGA using the "Internal Configuration Access Port (ICAP)". You use this by instantiating the ICAP_SPARTAN6 primitive and, when you want to, you instruct that to re-program the FPGA. This is described in the Spartan-6 Configuration User Guide (UG380), in the section titled "Reboot Using ICAP_SPARTAN6".