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Hercules™ Safety Microcontrollers Forum
Communicate with ARM7TDMI Core via DCC over JTAG (TMS470PSF)
GOAL: I'm trying to get past a few hurdles so I can communicate with the ARM7TDMI Core using the DCC (Debug Communications Channel) registers via JTAG.
1. Currently I've determined that you must select the TAP associated with the core and bypass the ICEPick. I've successfully performed this based on the information provided here http://processors.wiki.ti.com/index.php/ICEPICK
2. Once the Correct TAP is selected I can now communicate with the ARM Core, however, there are several scan chains (Sub scan chains, if you will) for the ARM Core as well. I believe that the scan chain I need to use in order to communicate with the DCC is the Scan Chain 2, "EmbeddedICE-RT Logic Programming".
3. I've performed what I believe, based on the ARM7TDMI Reference Manual, to be the process for selecting and activating Scan Chain 2
- Select Scan Chain 2
- Place Scan Chain 2 into "INTEST" mode to allow communication to and from the core.
1. When I perform the final step "INTEST" I get the ERROR LED on my demo board... unfortunately I cannot tell what the specific error is.
2. The Section in the ARMTDMI Manual for the DCC describes 3 32-bit registers, yet the Registers available for the EmbeddedICE-RT scan chain show 2 registers one of 6-bits and one of 32-bits.
Anybody with insight on how to access the core for Memory reads/writes in real-time would be much appreciated.
I had an opportunity to try something similar about a decade ago. I am a bit rusty, but I think I see one of your problems. TMS470P devices use the ARM7TDMI rev 3 CPU. Most of the ARM documentation available is referencing the ARM7TDMI rev 4 CPU. There were some differences between the revisions in regards to the Embedded ICE-RT logic.
If I look at a local copy of the ARM7TDMI rev 3 TRM from ARM (DDI0029G), it notes 2 32b registers and one 6b register. If I look at the most recent ARM TRM for ARM7TDMI (DDI0210B), it references rev 4 and notes 3 32b registers. Try reviewing the rev3 TRM from ARM and see if you get a bit further.
Did this take care of your question? Can I close this thread, please?
Although the suggestion was appreciated, the Documentation for the DCC was still not helpful regardless of the revision. The DCC was abandoned for what I was trying to accomplish since it was determined not to be real-time.
This thread can be closed from my perspective.
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