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elRey
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« on: March 14, 2016, 12:47:41 PM »
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Let me first ask when scanning DTC I might see P1103 008 vs P1103 035. How do I follow the disassembly to determine how the 008 is set vs the 035? And logic to set DTCs in general: I can find WHERE (in which func) P1103 is set: mov r12, #45h
calls 84h, SetDTCME75_846b3e But I don't understand WHY it's set solely based on the disassembled code. I get that the setDTC func uses the r12 and [r0+2]:  And that r12 is set right before calling the setDTC func, but the [r0xxx] statements confuse me. They're different before each setDTC func call:  And I get how to follow the decision tree to get to where [r0xxx] are set, but I can't match when/where/which [r0xxxx] is set to which [r0xxxx] is used for each setDTC func call. And what are the bfldh r2, #DTCFieldA_H0|DTCFieldB_H1|DTCFieldC_H2|DTCFieldD_H3, #DTCFieldD_H3
bfldl r4, #DTCBit_L1, #DTCBit_L1
calls doing exactly?   Where #45h Error Class is used, what do I look for to find what is being passed into the setDTC func as [r0+2] ? snippet from first img: mov r4, [r0+2]
mov [-r0], r4
mov r12, #45h
calls 84h, SetDTCME75_846b3e
Thanks in advance. I know I'm asking for a lot. Rey |
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« Last Edit: March 14, 2016, 12:49:59 PM by elRey »
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elRey
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« Reply #1 on: March 14, 2016, 04:05:54 PM »
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I just realized I've forgotten r0 and [r0] are not the same thing. I'll try looking it over again with that in mind.
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phila_dot
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« Reply #2 on: March 14, 2016, 04:15:07 PM »
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Follow the stack and look at the bitfield masks in hex
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phila_dot
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« Reply #3 on: March 14, 2016, 07:57:34 PM »
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Also %DFPM breaks down the DTC bits
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elRey
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« Reply #4 on: March 15, 2016, 06:42:34 AM »
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Thank you phila_dot. Reading that section now. As for following the stack, easier said than done for those of us not having a background computer science  |
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nyet
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« Reply #5 on: March 15, 2016, 11:52:01 AM »
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Thank you phila_dot. Reading that section now. As for following the stack, easier said than done for those of us not having a background computer science FWIW it isn't easy for anyone. |
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ME7.1 tuning guideECUx PlotME7Sum checksumTrim heatmap toolPlease do not ask me for tunes. I'm here to help people make their own. Do not PM me technical questions! Please, ask all questions on the forums! Doing so will ensure the next person with the same issue gets the opportunity to learn from your ex
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phila_dot
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« Reply #6 on: March 16, 2016, 08:08:44 AM »
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Ask any specific questions that you have, it's alot to try and do a whole writeup on your OP.
It's a top down stack.
[-r0] pushes onto the bottom (adds underneath)
[r0] accesses the current (bottom)
[r0+n] accesses n from the bottom
[r0+] pops off the bottom
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elRey
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« Reply #7 on: March 16, 2016, 12:29:18 PM »
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That is great info in and of itself! Thanks.
What's the difference between r0 and [r0]?
Or are all your examples indirect references using stack and same could be done as direct access to stack values without square brackets?
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« Last Edit: March 16, 2016, 12:31:45 PM by elRey »
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phila_dot
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« Reply #8 on: March 16, 2016, 01:43:05 PM »
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It's a stack pointer, so [r0] is accessing the data stored and r0 is the stack pointer (memory address) itself. As seen at the end of the function, this is resetting the stack pointer. |
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elRey
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« Reply #9 on: March 16, 2016, 03:20:46 PM »
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[-r0] pushes onto the bottom (adds underneath)
[r0] accesses the current (bottom)
[r0+n] accesses n from the bottom
[r0+] pops off the bottom
Ok, in your previous example if a added a line between [r0 + n] And [r0+] as such: [-r0] pushes onto the bottom (adds underneath) [r0] accesses the current (bottom) <- is it bottom because of previous line? [r0+n] accesses n from the bottom [r0] accesses the current (n from bottom?)[r0+] pops off the bottom When does the pointer change? Any time there's - or + or func r0, xxx ? |
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phila_dot
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« Reply #10 on: March 16, 2016, 05:26:46 PM »
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mov r4, #1h
mov [-r0], r4
Stack
1
----------------
mov r4, #2h
mov [-r0], r4
Stack
1
2
------------------
mov r4, #3h
mov [-r0], r4
Stack
1
2
3
-----------------
mov r4, [r0]
Stack
1
2
3
r4 == 3
-----------------
mov r4, #4h
mov [r0], r4
Stack
1
2
4
-------------------
mov r4, [r0+4]
Stack
1
2
4
r4 == 1
------------------
mov r4, #5h
mov [r0+4], r4
Stack
5
2
4
-------------------
mov r4, [r0+2]
Stack
5
2
4
r4 == 2
-----------------
mov r4, [r0+]
Stack
5
2
r4 == 4
----------------
add r0, #2h
stack
5
Edit: Corrected
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« Last Edit: March 17, 2016, 10:17:02 AM by phila_dot »
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elRey
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« Reply #11 on: March 16, 2016, 07:13:40 PM »
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mov r4, #1h
mov [-r0], r4
Stack
1
----------------
mov r4, #2h
mov [-r0], r4
Stack
1
2
------------------
mov r4, #3h
mov [-r0], r4
Stack
1
2
3
-----------------
mov r4, [r0]
Stack
1
2
3
r4 == 3
-----------------
mov r4, #4h
mov [r0], r4
Stack
1
2
4
-------------------
mov r4, [r0+2]
Stack
1
2
4
r4 == 1
------------------
mov r4, #5h
mov [r0+2], r4
Stack
5
2
4
-------------------
mov r4, [r0+1]
Stack
5
2
4
r4 == 2
-----------------
mov r4, [r0+]
Stack
5
2
r4 == 4
----------------
add r0, #1h
stack
5
Golden. Thank you so much for taking the time to do that!!!! |
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DT
Full Member
Karma: +20/-1
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Posts: 184
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« Reply #12 on: March 17, 2016, 03:17:59 AM »
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i think phila_dot forgot about word and byte in his writeup
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« Last Edit: March 17, 2016, 03:33:33 AM by DT »
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phila_dot
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« Reply #13 on: March 17, 2016, 05:55:47 AM »
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Good catch, posting quickly from my phone and trying to use simple examples.
I used all words and then byte offsets.
I will correct them when I get a minute.
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« Last Edit: March 17, 2016, 06:15:13 AM by phila_dot »
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dream3R
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« Reply #14 on: May 02, 2016, 06:52:05 PM »
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I just realized I've forgotten r0 and [r0] are not the same thing. I'll try looking it over again with that in mind.
pointers |
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