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Old 21 May 2018, 06:23   #1
Dipski
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DKB Cobra Dead FPGA

I've got a DKB Cobra which has a dead Xilinx XC3130A that I've removed, I haven't programmed an FPGA before so thought I'd see if anyone can help. If I use the install disk from;

http://amiga.resource.cx/exp/cobra

will that flash a blank (new) FPGA or will I need to program it before soldering it onto the card?
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Old 21 May 2018, 07:44   #2
cpiac64
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the disk update only eeprom not the xilinx

you need solder old xilinx

i have repaired some cobra whit new connector or a washed connector with ultrasong
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Old 21 May 2018, 09:09   #3
ajk
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I don't think the Xilinx chip holds the program within itself, what happens is that during boot it will load it from the EEPROM. From the datasheet:

Quote:
The program data resides externally in an EEPROM, EPROM or ROM on the application circuit board, or on a floppy disk or hard disk. On-chip initialization logic provides for optional automatic loading of program data at power-up.
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Old 21 May 2018, 09:24   #4
Toni Wilen
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FPGA code most likely is in boot ROM flash chip. Every FPGA chip equipped DKB board ROM dump I have seen has few kilobytes of "random" looking data at the end of the ROM image.
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Old 21 May 2018, 12:04   #5
RedskullDC
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Quote:
Originally Posted by Toni Wilen View Post
Every FPGA chip equipped DKB board ROM dump I have seen has few kilobytes of "random" looking data at the end of the ROM image.

Xilinx XC3000 series chips allow configuration from a Byte wide source, either from address $0000 up, or from $FFFF down:


Table 1: Configuration Mode Choices
M0 M1 M2 CCLK Mode Data
0 0 0 output Master Bit Serial
0 0 1 output Master Byte Wide Addr. = 0000 up
0 1 1 output Master Byte Wide Addr. = FFFF down
1 0 1 output Peripheral Byte Wide
1 1 1 input Slave Bit Serial


From Toni's observation, sounds like it is configured as $FFFF down mode, and initialises the FPGA from the code at the end of the ROM image.

Good luck with it

Cheers,
Red
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Old 21 May 2018, 13:49   #6
Dipski
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Brilliant, thanks guys - that's great news! I'll drop a new Xilinx chip on it and hopefully it's all up and running again.
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