C166: SINGLE STEP WITH ULINK JUMPS TO ADDRESS 20H

Information in this article applies to:

• C166 Version 5.05

QUESTION

I am using ULINK to debug my application on an Infineon XC16x microcontroller. I download the application into off-chip RAM to be able to use an unlimited number of software breakpoints. Occasionally, I see that the program counter moves to address 0x000020 with a Step Into command. Continuing from this address makes no sense. What's going on?

ANSWER

This is a side effect of the branch prediction unit. ULINK uses the DEBUG instruction for software breakpoints in RAM. This DEBUG instruction is cached by the 'branch prediction unit' when CPUCON1.1 is set and the breakpoint was set on a JMP instruction.

In order to avoid this problem you can either turn off the branch prediction unit (CPUCON1.1) in your START_V2.A66 configuration file or you can use an updated UL2OCDS driver which is attached to this knowledgebase article. The attached ZIP file must be extracted into the \Keil\C166\BIN folder. This updated driver is included in every C166 version newer than 5.05.

SEE ALSO

• ULINK: OCDS: PROGRAM COUNTER MOVES TO INCORRECT VALUES

ATTACHED FILES

Request the files attached to this knowledgebase article.

Last Reviewed: Wednesday, June 15, 2005