OBD1 8bit High Cam RPM
This formula is used to convert values in the high cam table scales to realworld RPMs. If ''x'' is an 8bit highcam scale RPM value, Hi Cam RPM(''x'') = 1875000''x'' / 53248 53248=D000h.
Adapted from pgmfi.org wiki
This formula is used to convert values in the high cam table scales to real-world RPMs. If ''x'' is an 8-bit high-cam scale RPM value,
- Hi Cam RPM(''x'') = 1875000*''x'' / 53248
53248=D000h. Here is how it's calculated using standard integer fixed-point math tricks: | |MOV er2, 0ach|; 0805 0 02 00 B5AC4A | |MOV er0, #0d000h|; 0808 0 02 00 449800D0 | |CLR A|; 080C 1 02 00 F9 | |DIV|; 080D 1 02 00 9037 | | |; DIV = (er0, A) <-- (er0, A) / er2; in this case, 0xd0000000 / (1875000/RPM) | | |; using bytes instead of words, (r1,r0,Ah,Al) <-- (r1,r0,Ah,Al) / (r5,r4) |||''... store the high bit of A, decide whether the divide overflowed, etc...'' | |LB A, r0|; 0817 0 02 00 78 | | |;r0 is the least significant byte of er0, which is the most significant word of the quotient! | |JNE label_081f|; 0818 0 02 00 CE05 |||''... overflow conditions, etc...'' |label_081f:|STB A, 0aah|; 081F 0 02 00 D5AA
Credits and source
Source Adapted from OBD1 8bit High Cam RPM on pgmfi.org wiki. Licensed under CC BY-NC-SA 1.0.