FPGA芯片：XC6SLX150，FLASH M25P64,用JTAG可以烧写FPGA，但是不能烧FLASH，
impact给出的信息如下：
elected part: M25P64
Unprotect sectors: FALSE
INFO:iMPACT - Current time: 2015/11/30 16:30:33
PROGRESS_START - Starting Operation.
Maximum TCK operating frequency for this device chain: 25000000.
Validating chain...
Boundary-scan chain validated successfully.
'1': SPI access core not detected. SPI access core will be downloaded to the device to enable operations.
INFO:iMPACT - Downloading core file D:/Xilinx/14.7/14.7/ISE_DS/ISE/spartan6/data/xc6slx150_spi.cor.
'1': Downloading core...
LCK_cycle = NoWait.
LCK cycle: NoWait
done.
'1': Reading status register contents...
INFO:iMPACT:2219 - Status register values:
INFO:iMPACT - 0011 1100 1110 1100
INFO:iMPACT:2492 - '1': Completed downloading core to device.
'1': IDCODE is 'ffffff' (in hex).
'1': ID Check failed.
INFO:iMPACT:2488 - The operation did not complete successfully.
INFO:iMPACT - SPI Device not found.
INFO:iMPACT:2488 - The operation did not complete successfully.
INFO:iMPACT - '1': Flash was not programmed successfully.
PROGRESS_END - End Operation.
Elapsed time =      4 sec.
INFO:iMPACT - Current time: 2015/11/30 16:31:27
PROGRESS_START - Starting Operation.
Maximum TCK operating frequency for this device chain: 25000000.
Validating chain...
Boundary-scan chain validated successfully.
'1': IDCODE is 'ffffff' (in hex).
'1': ID Check failed.
INFO:iMPACT:2488 - The operation did not complete successfully.
INFO:iMPACT - SPI Device not found.
INFO:iMPACT:2488 - The operation did not complete successfully.
INFO:iMPACT - '1': Flash was not programmed successfully.
PROGRESS_END - End Operation.
Elapsed time =      0 sec.

用示波器测量Flash的信号：1.黄 {MOD}：时钟
2.蓝 {MOD}：片选
3.红 {MOD}：Din
4.绿 {MOD}：MOSI
信号很怪异，片选拉低后，MOSI先于时钟给出，时钟断断续续，片选很快就拉高了