747 -> 730 VSS PPM question... - Third Generation F-Body Message Boards

V8Astro Captain · 09-06-2005, 02:22 PM

I'm using a DRAC with my 730 conversion. I'm inputting vehicle speed from the DRAC to C6 on my 730. My question is what happens to the VSS PPM setting at $0015?

My assumption is that this setting is for gears, tires and whatnot. My DRAC takes care of this so what does $0015 do now?

JP86SS · 09-06-2005, 07:30 PM

My curiosity is peaked

I have no info on C6 on the 730 or address $0015. (not used in both cases in my $8D stuff)

What are you working with ?

V8Astro Captain · 09-06-2005, 11:58 PM

I'm retarded...sorry it's $8015

Code:

L8015: FCB 230 ; PULSE/MILE RD SPD CONST
; ARG = 921600/VAL

C6 isn't used on the '730. With some help and alot of searching I found that the Sy/Ty '749 used C6 as speedo input from a DRAC. It's the best thing I could come up with since my VSS is DC 2000 ppm and the '730 expects an AC 4000 ppm signal.

Best info is here
http://www.thirdgen.org/techbb2/show...=&pagenumber=1

Z69 · 09-07-2005, 02:38 AM

Depends on which sensor you pick

Code:

;--------------------------------------------------
; Vss CALCULATION
;--------------------------------------------------
LBF7D:        ldab    *L008D                  ; GET Vss COUNT                                ; CRef: 0xBF78
;
; CK AFR OPT WD 3, 0101 0010
; b6, 1 = MAG SPD SENSER INSTALLED
;
              ldaa    L8018                   ; 0101 0010, AFR OPT WD 3
              bita    #0x40                   ; b6
              bne     LBF9A                   ; BR IF b6, MAG SENSOR
                                              ; ... else
;
; OPTICAL SENSOR
;
              ldx     #0x01CD                 ; VAL = 461, 461 = 1 RD SPD PULSE
              decb                            ;
              beq     LBF95                   ; BR IF EQUAL 1 Vss PULSE
                                              ; ... else
              ldx     #0x039A                 ; VAL = 922, 922 = 2 RD SPD PULSE'S
              decb                            ;
              beq     LBF95                   ; BR IF EQUAL 2 Vss PULSE'S
                                              ; ... else
              ldx     #0x0566                 ; VAL = 1382, 1382 = 3 RD SPD PULSE'S
LBF95:        pshx                            ; SAVE MULT CONST                              ; CRef: 0xBF8A,0xBF90
              pula                            ; CONST TO A Reg
              pulb                            ;
              bra     LBF9E                   ; BRANCH ALWAYS
;
; MAG SENSOR
;
LBF9A:        ldaa    L8015                   ; PULSE/MILE RD SPD CONST, 230d (4006 PPM)     ; CRef: 0xBF84
                                              ; ARG = 921600/VAL, (4006 PPM)
              mul                             ; (A * B = D)
LBF9E:        ldx     *L008B                  ; GET CURRENT Vss COUNT                        ; CRef: 0xBF98
              fdiv                            ; D / X (16 bit)
              pshx
              pula
              pulb                            ;  The stack pointer is incremented 
              tstb                            ; Test if Positive Value
              bpl     LBFAB                   ; BR IF LSB Less Than 128, (0x80)
                                              ; ... else
              inca                            ; ROUND UP
              bne     LBFAB                   ; IF NO OVERFLW
                                              ; ... else
              deca                            ; PREVENT OVERFLOW
;
; FILTER Vss,

V8Astro Captain · 09-07-2005, 08:38 AM

I have my bin set for the optical VSS.

I know nothing about code, but from what I see $8015 isn't mentioned in the optical part of the code you posted.

So what happens?

Code:

; VAL = 461, 461 = 1 RD SPD PULSE

I'm guessing that this play a large part.

Thanks for all your help Z69

JP86SS · 09-07-2005, 10:02 PM

An old post about adjusting the bits at the instrument panel divisor ($8014)
http://www.thirdgen.org/techbb2/show...t=reads+96+mph

From the code snippet that Z69 posted, the Optical sensor value is used (#0x01CD ; VAL = 461, 461 = 1 RD SPD PULSE)
and the value for the mag sensor ($0015) is ignored.

To adjust the value IF your readings are incorrect, the hard coded hex value would need to change using TP or any hex editor.
The actual location for the value is BF87= $01, BF88=$CD
Remember the addressing starts at $8000.
I don't know what to tell you except be careful and check your results before trusting a new value on a long trip.

Z69 · 09-08-2005, 12:42 AM

JP's correct, or we both read it the same way at least.

Also, there are actually 3 hard coded values for the optical from above. Based on the # of pulses. 1 or 2 or 3. Not sure how this works.

Code:

ldx     #0x01CD                 ; VAL = 461, 461 = 1 RD SPD PULSE
ldx     #0x039A                 ; VAL = 922, 922 = 2 RD SPD PULSE'S
ldx     #0x0566                 ; VAL = 1382, 1382 = 3 RD SPD PULSE'S

The mag code and optical use different values for the calc.
One of the 3 above divided by L008B (VSS cnt)
Or L008D (Diff VSS) times L8015 Divided by L008B (VSScnts).
After this calc, the code appears to be the same regardless of sensor selected.

JP86SS · 09-08-2005, 08:58 PM

Actually it looks to me like GM had some trouble making the optical read when just starting to move or at faster input rates.
That's the only thing I can make from it as to why they put default values in the caculation when during a single loop.
Maybe I'm looking at it wrong but looks to me like:
if 1 pulse is read (per scan), use 461
if 2 pulses are read (per scan), use 922
if 3 pulses are read (per scan), use 1382

Could be that this is the multiplier used to calculate when counting allot of pulses during a single program scan loop. (makes more sense to me that way)
It must be difficult or delayed to transfer in the signals (as a count) fast enough from the optical input as compared to the mag pickup counter.
The mag counter just inputs and doesn't seem to need this.