I'm not sure how that particular script / firmware works, but in general, a single read/write action in the ROACH2 QDR transfers 144 bits. The granularity of the python read writes is 32-bits, so what actually happens is that a read from casperfpga grabs 144 bytes, carves it up into 4x36 bit words, throws away the most significant 4 bits of each chunk, and then returns the appropriate 32 bits. Note that this makes writes from software particularly tricky -- if you don't write in bursts of 16 bytes, (aligned to 16-byte addresses) there is a very high probability that things will not work the way you want.
These lines ( this <https://github.com/realtimeradio/mlib_devel/blob/ef054be0ba14eac4f2e79b998d7af2e9ef918be6/xps_base/XPS_ROACH2_base/pcores/opb_qdr_sniffer_v1_00_a/hdl/verilog/async_qdr_interface36.v#L31> and this <https://github.com/realtimeradio/mlib_devel/blob/ef054be0ba14eac4f2e79b998d7af2e9ef918be6/xps_base/XPS_ROACH2_base/pcores/opb_qdr_sniffer_v1_00_a/hdl/verilog/async_qdr_interface36.v#L87> ) show how the 32-bit selection is implemented. The commit message associated with the second line linked says "MSb 32 bits are read first, followed by bits 32 to 63". I'm not sure how this relates to the convention assumed in the firmware interface. I would imagine the intention is that for a QDR write (which takes 2 clock cycles and writes 64 bits on each) the logic is (with addressing in 32-bit words): First write cycle: most significant bits = word 0; least significant bits = word 1 Second write cycle: most significant bits = word 2; least significant bits = word 3; I don't know of many occasions when both the CPU and firmware QDR interfaces are both used, so it's very possible that the relationship between the firmware and software interfaces is either not as intended, or is as intended but with an odd, undocumented mapping. Hopefully the above helps point you in the right direction(?) Hopefully it doesn't just add to the confusion(?) Cheers Jack On Mon, 21 Dec 2020 at 10:12, zhang laiyu <[email protected]> wrote: > Hi > > Thanks for your help. > > The firmware and python script had worked (qdr_basic and qdr_counter).I > can get the plot. But I can not understand the PPC readout script in > qdr_counter.py thoroughly .The address is really weird. After studying > the wiki of the CASPER QDR yellow block and datasheet of the QDR > chip(CY7C2565KV18), I still can not understand the python script very well. > Why the 'PPC data' was picked like that? Could you give me some suggestion > about where can I find more clear information about the addree of QDR > interface to PowerPC? > > > > > Cheers! > > >------------------------------------------------------------------------ > ZHANG Laiyu > Phone(China) 010-88233078 > Cellphone(China) 13681385567 > E-mail: [email protected] > Address: 19B Yuquan Road,Shijingshan District,Beijingļ¼China > Department: Center for Particle Astrophysics > Office: Astrophysics Building 205 > > Institute of High Energy Physics, CAS > web: http://www.ihep.cas.cn <http://www.ihep.ac.cn/> > > >------------------------------------------------------------------------ > > > > > > > > > > > > > > > > > > > > > * <[email protected]>* > > > <http://isdc.unige.ch/~produit> > > -- > You received this message because you are subscribed to the Google Groups " > [email protected]" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/606c0c11.e7c3.17684c842a5.Coremail.zhangly%40ihep.ac.cn > <https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/606c0c11.e7c3.17684c842a5.Coremail.zhangly%40ihep.ac.cn?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "[email protected]" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/a/lists.berkeley.edu/d/msgid/casper/CAG1GKSkVM8Y2Odu%2BW%2BjOMSLbZw8kaOq5jhzUEc_hkZtS2Jdmcg%40mail.gmail.com.
