I am trying to solve the one last problem i have in my conversion to a '8625 PCM. The only thing i cannot get to work is the TCC. One of the biggest problems is a lack of 40 pulse/rev trans output shaft speed sensor and DRAC.
There is a flag that can be set to tell the PCM if the speed signal is to come from a DRAC or not, this flag is at $5A02, bit4.
I'd like to know where it looks for the speed if this bit is set to 1. Can anyone have a skim over this and tell me?
I've come a long way, but this step is beyond me. TIA!


; CK IF XMISH SPD IS TO COME FROM DRAC
;
B081: LDAA #$10 ; b4 0 = OUTPUT SPD FM DRAC
B083: BITA L5A02 ; XMISH MODE WD, 0010 0001,
B086: BEQ LB08F ; BR IF b4 (FM DRAC)
; ... else
B088: LDX #$3FC6 ; READ SPEED CNT'R
B08B: LDY #$3FF8 ; PA1 TMR

B08F: LB08F SEI ; TURN OFF INTERUPTS
B090: LDD 0,X ; GET Rd spd pulse cntr, *** rd spd pulses
B092: JSR LEFFE ; SHORT DELAY
;
B095: PSHY ;
B097: LDY 0,Y ; B Ctr, LN NEW B CNT'R VAL
B09A: JSR LEFFE ; SHORT DELAY
;
B09D: CPD 0,X ; CMP W/Rd spd pulse cntr, *** rd spd pulse
B0A0: BEQ LB0AD ; BR IF EQ
; ... else
B0A2: JSR LEFFE ; SHORT DELAY
;
B0A5: PULY ;
B0A7: LDY 0,Y ; B Ctr, LN NEW B CNT'R VAL
B0AA: INCB ;
;
B0AB: BRA LB0AF ;
;
B0AD: LB0AD INS ; INCR STX
B0AE: INS ;
;

 

B081 load 00010000 to A
B083 and word L5A02 and A

IOW 00010000 and 00100001 where each bit is anded and 1 and 1 = 1, 0 and anything = 0

The result of above = 00000000 or 0

B085 Branch if equal to 0

Here we jump around the speed counter.

B088 load speed counter.

HTH

John