MAX V, USB Blaster Rev C, chain is broken, 1.8V

[JPA]

Have a feeling this is something simple/stupid...trying to bring up a new MAX V design and program it with a USB Blaster (Linux) and it says chain is broken and it can't detect device.

Same PC hardware works if I'm talking to a MAX 10 Eval board.

Okay, maybe I screwed up the design despite trying to follow all the examples I could find.  But I can see activity on both the TDO and TDI when I debug the chain.  Signals look good and 1.8V.  VCCINT is 1.8V and VCCIO1 is 1.8V, VCCIO2 is 3.3V.  

Anything obvious that I'm doing wrong?  Any suggestions on how to debug it further?  Two boards doing the same thing.  

John

[YuanLi_S_Intel]

Hi JPA,

Are you using MAX V Development Kit? If it so, can you try to change all the switches to default position and try again?

Regards,

Bruce

[JPA]

Not using MAX V Development kit, this is a new custom design.   I do have a MAX 10 Dev kit available, and the PC software/hardware works with it.  So the differences between working and not working are MAX 10 vs MAX V,  Dev kit vs custom design,  3.3V interfacing vs 1.8V interfacing.  

The fact that I'm getting signals on TDI and TDO makes me think that the problem is in the 1.8V interfacing, but without a schematic for the USB Blaster, it's hard to know.   It could certainly be a problem with my design.

John

[JPA]

Attaching a reduced schematic in case it helps.  

[YuanLi_S_Intel]

Since you are using VCCIO1 = 1.8V. Have you checked your TCK Frequency? Can you try to change that to lower frequency?

https://www.intel.cn/content/dam/www/programmable/us/en/pdfs/literature/hb/max-v/max5_handbook.pdf#page=77

[JPA]

Thanks, but it turns out that the the USB Blaster I was using must be a clone.  Took it apart, and while the initial LC buffer should work at 1.8V and is being powered by the target, the next device in the signal chain is a PIC18 powered off the USB 5V, and AFAICT, the 1.8V best case Voh won't meet the input specs of the PIC.  Bought a Terasic Blaster and the chain is fine and the device programs.  

Thanks for responding,

JPA

[YuanLi_S_Intel]

I am glad it works now. Cheers.