06-23-2012 12:07 PM
We have a problem with Spartan-3E (XC3S500E, PQ208) configuration in slave parallel mode. We have already used successfully such a configuration method with Spartan-3 (XS3S400 and XC3S200) with different microcontroller (LPC2148), even on a two-sided PCB. Currently we are using TMS320F28335 with much shorter traces and 4-layer PCB. The only difference is in HSWAP pin, which was pulled down in the old setup, and which is pulled high currently.
We can successfully send the configuration data using slave serial mode with one data line, but in the same circuit, when all 8 data lines are used in parallel mode, there is no response from FPGA during data upload, as it would not synchronize at all. It does not even drop INIT_B when bitstream is plainly incorrect (e.g., for different Spartan chip model).
We have uploaded, using serial mode, a test circuit into FPGA, which echoed the states on D0..D7, CSI_B and RDWR_B pins to other pins that we can test with an oscilloscope, that all these pins can receive signals from the microcontroller.
What else can be the reason, that FPGA seems to ignore all data sent in parallel mode, while it works in serial mode?
Thanks in advance,
Michal H. Tyc
DiagNova Technologies, Wroclaw, Poland
06-23-2012 01:09 PM
Suggest you post your board-level schematic.
-- Bob Elkind
06-26-2012 11:41 PM
We attach simplified schematic (all MCU-FPGA connections are left).
Some additional information: CCLK was tested from below 0.5 MHz to above 10 MHz with the same results, no ringing can be seen on an oscilloscope (and serial mode, as we wrote, works correctly). Supply voltages were measured as 1.23 V (Int), 3.46 V (IO -- intentionally made higher because of connected A/D converters), 2.58 V (Aux). All supply pins have decoupling capacitors.