Why does em2xx_load (or em2USBLoad) keep saying "Shift Register All 0's" or "LOADB stuck low"?

At times customers have reported seeing unexpected output from the EM2xx Utilities (em2xx_load/patch/read) or their EM2USB counterparts, where the output contains a repeated message like:

 XAP2= DbgEna Shift register is all 0's
 XAP2= Stop Shift register is all 0's
 XAP2= DbgEna Shift register is all 0's
 XAP2= Reset Shift register is all 0's
Shift register is all 0's
Shift register is all 0's
Shift register is all 0's

…or something like this:

 XAP2= DbgEna LOADB stuck low
 XAP2= Stop LOADB stuck low
 XAP2= Reset LOADB stuck low
 XAP2= Issuing SW_RESET
 XAP2= DbgEna LOADB stuck low
 XAP2= Stop LOADB stuck low
 XAP2= Reset LOADB stuck low
LOADB stuck low
LOADB stuck low
LOADB stuck low
LOADB stuck low
LOADB stuck low
LOADB stuck low

In general, these sorts of errors point to communication problems across the SIF programming interface, which may either be due to:

• a faulty InSight Adapter (ISA) or InSight USB Link device
• a faulty 10-pin InSight Port cable
• a faulty board (missing/intermittent ground connection, particularly to the ground pad underneath the chip; bad solder joints to pins due to footprint or solder reflow issues)
• board not having appropriate protection around SIF programming signals at the InSight Port

In respect to the latter, optimal performance on the SIF bus can be achieved by ensuring that the following components are present in the InSight Port circuit:

• Pull-up on nSIF_LOAD; this value (R2) should be 560 ohms (a change from older designs)
• Reset glitch filter on nRESET (R1 10K ohms, C1 10nF)
• Pull-down on SIF_MOSI (R4 @ 10kOhm)

In these cases, Ember recommends double-checking the design against the component values above and also swapping out various pieces of the system (board instance or board type, cable, ISA) to see if the problem follows one particular item.

If an Ember tool seems to be the source of the failure, you can contact Ember Support to ask about the possibility of a Return Materials Authorization (RMA).