Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Error in JTAG chain before reprogramming

I'm trying to reprogram a MAX II CPLD with USB Blaster in JTAG mode. When I click Auto Detect appears error message “Unable to scan device chain. Can’t scan JTAG chain.” Testing JTAG chain with...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

--- Quote Start ---

Unable to scan device chain. Can’t scan JTAG chain

--- Quote End ---

The message is typically caused by a discontinuos JTAG chain = no response on TDI after a larger number of TCK transitions. Thus it's not very specific, can mean a defective programming adapter, broken cable, wrong PCB wiring, defective device, missing power supply.

If the programming adapter is working correctly (also the LED would be active during access), you should at least see initial signal bursts on the USB Blaster output signals.