Readback on Vritex2, help me.

[wei ming]

hi,

I am now doing a readback on the virtex2 device(xc2v1000). I have read
the application note 138,139. But it's for virtex. I suppose it's the
same with virtex2. I have still some question about it,

1. Load the CFG_IN instruction into the JTAG IR, then go to SDR(shift
data to register). I should first shift a sync word(aa995566)?

2. the frame size to readback. for xc2v1000, one frame length is 3392
bit. I think it's same like virtex. For only one frame readback, It
read back first the pad frame(3392 bit), then it's the frame we
want.(3392 bit). so I think the frame size is 3392*2/32 = 212(d4h). is
it right?

3. How many times should I flush the command pipe? I think 2 times 32
bits of 0 are sent to flush the command pipe, because the JTAG
register is 64 bit. is it right?

4. Is there a pad word in front of frame?

I write the c code for readback. It's the command sequence ,

1. 0xAA995566; Synchronization word
2. 0x30002001; write to FAR register
3. frame addr; from .ll file
4. 0x30008001; write to CMD register
5. 0x00000004; Active RCFG
6. 0x280060d4; Number of word to readback (d4h = 212)
7. 0x00000000; Flush command pipe with 32 bits of zeros.
8. 0x00000000; Flush command pipe with 32 bits of zeros.

is that right?

Thank you for reading. Any information about it is welcome. Thanks in
advance.

Wei