Quirks!

[RobertISaar]

busy hacking through some 94-95 3800 code(5B), found something that i forgot about seeing in a derivative before.... 1FA and 2E are basically slimmed down versions of 5B, but their applications were a bit different... 1FA/2E was used on 3100 and 3.4DOHC, while 5B was used on the 3800. i don't work with the 90V6 engines very much, which is why i saw it on the 60V6 application first.

anyways, plowing through the calibration and i found something odd with the main spark tables... here's a quick rundown of the code concerning it:

check if above 4800RPM
if so, lookup high RPM spark table (2D) (8115)
if not, lookup main spark table (8022)

well... the main spark table only actually goes to 4400RPM... but since the 4800 and up table is immediately after the main table, it actually lines up and will be looked up as another row. the code doesn't attempt to limit reading above 4400RPM either...

so, it acts like a single 400-4800RPM table, but in the code it's actually a 400-4800RPM table and a 4800+ RPM table.... essentially, the extra lookup for 4800+ is pointless since it will already be used.



so, anybody else find odd things they want to discuss/share?

[EagleMark]

Hard to compete with you but I'll play and maybe learn something?

$4F XDF Fuel VE table goes to 5200 RPM, but the assembly only goes to 4800? Somone started at 400 RPM instead of 0 RPM.

Odd? Have you ever seen how much Air managmant code is in a $6E assembly? And I can't find a way to turn it off? In $42 it's just a temp on and timer...

Since I'm stating to understand looups and sub routines how about a lesson on the commands? I just grabbed this piece and BOLD, Italic and UNDERLINED some examples.

                 ;--------------------
                ; LK UP  ACCEL ENRICH 
                ; vs Diff TPS 
                ; ** PUMP SHOT **
                ;--------------------
D775:            LDAA    #255
D777:  LD777     LDX     #$D312         ; ACCEL ENRICH vs Diff TPS TBL
                                        ; Contrib vs Diff TPS TBL
D77A:            JSR     LFAD7          ; 2D LK UP 
 ;                                                            
D77D:            LDAB    L00DF
D77F:            ORAB    #$10           ; BIT 4
D781:            BRA     LD786
 ;                                                            
D783:  LD783     CLRA    
D784:            ANDB    #$EF       ; 0111 1111
D786:  LD786     STAB    L00DF
D788:            STAA    L0058      ; BPW, MSB
D78A:            STAA    L009A
D78C:            CLRA    
D78D:            LDAB    L00DF
D78F:            BITB    #4         ; BIT 2
D791:            BEQ     LD796
 ;                                                            
D793:            LDAA    LD28F      ; 183 Usec, BPW ADDER TO BPW WHILE 
                                    ; IAC IS OPENING
                                    ; VAL MSEC = 16.384 
                                    
D796:  LD796     ADDA    L0058      ; BPW, MSB
D798:            BCS     LD79E
                                    ; ... else                               
D79A:            ADDA    L0059      ; BPW, LSB
D79C:            BCC     LD7A0
                                    ; ... else    
D79E:  LD79E     LDAA    #255       ; MAX LMT
D7A0:  LD7A0     BEQ     LD7BE
 ;                                                            
D7A2:            LDAB    L0098
D7A4:            MUL     
D7A5:            LSRD               ; DIV BY 8
D7A6:            LSRD    
D7A7:            LSRD    
D7A8:            ADDD    L0096
D7AA:            STD     L0096
D7AC:            LDAB    L0006
D7AE:            LDAA    L000D
D7B0:            BITA    #$40       ; BIT 6
D7B2:            BNE     LD7B6
                                    ; ...... else                         
D7B4:            ORAB    #8
D7B6:  LD7B6     ORAA    #$C0       ; 1100 0000
D7B8:            ORAB    #1         ; BIT 0
D7BA:            STAB    L0006
D7BC:            BRA     LD7C2
                                                            
D7BE:  LD7BE     LDAA    L000D
D7C0:            ANDA    #$BF       ; 1011 1111
D7C2:  LD7C2     STAA    L000D
D7C4:            LDAB    L0072
D7C6:            BITB    #2         ; BIT 1
D7C8:            BEQ     LD7DD

[RobertISaar]

i don't see anything bolded? the [ code ] command seems to disable a lot of formatting.

AIR management should be able to be disabled completely with relative ease.... there have to be calibration scalars that could be manipulated to remove it entirely.

[jim_in_dorris]

I'm not sure if I see it correctly myself, but it looks like this is highlighted. If I may.

LDAA #255
D777: LD777 LDX #$D312 ; ACCEL ENRICH vs Diff TPS TBL
; Contrib vs Diff TPS TBL
D77A: JSR LFAD7 ; 2D LK UP ;
D77D: LDAB L00DF

LDAA and LDAB are Load Accumulators A and B.
LDX is Load index register X.
and JSR is Jump to subroutine.

What that piece of code is doing is loading accumulator A with $FF(256), loading the index register X with the address of the routine it wants (ACCEL ENRICH vs Diff TPS TBL)
then jumping to that subroutine to do a lookup. on return it then loads the B accumulator with the contents of $DF which is a status flag most likely. I'm not looking at the
hac of whatever piece of code that come from, but I feel confident that is what is happening

[RobertISaar]

more quirks from 5B....

the IAT correction to spark advance table.... instead of using normalized IAT, it's using raw A/D counts..... ???? it also has an upper limit of $D1 counts, not $D0 as expected... this complicates things a bit to try and get everything labeled correctly in the XDF.

so, within an hour or so of hacking/commenting, i've run across two really big mistakes in 5B... this one can be fixed with a single byte change, the other requires a bit of branching. wonder what else i'll find.

[EagleMark]

That was hard to see bold, I changed it to bold, Italic and underline... but Jim caught it and now I can spend some time with that info!

I don't want to hijack but I need some help and it's Quirk related.

BJYK has Mode 4 commands in the hex starting at $1800, BJYL and the available dissasmbly do not. What does Mode 4 do and how would it affect whatever?

  Location of ALDL mode 4 jump table and code in PROM
;
;~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
;
;-Not present in this calibration, dummy RTS table provided for this disassembly
;
 ORG $1800  
;
L1800 NOP    ;
 NOP    ;
 RTS    ;Return
;
L1803 NOP    ;
 NOP    ;
 RTS    ;Return
;
L1806 NOP    ;
 NOP    ;
 RTS    ;Return
; 
L1809 NOP    ;
 NOP    ;
 RTS    ;Return
;
L180C NOP    ;
 NOP    ;
 RTS    ;Return
;
L180F NOP    ;
 NOP    ;
 RTS    ;Return
;
L1812 NOP    ;
 NOP    ;
 RTS    ;Return
;
L1815 NOP    ;
 NOP    ;
 RTS    ;
;