It appears Scantool can clear BLM through mode 4 request
Status bit b4 @ $0045 can also initiate BLM reset.
Among other things, BLM will not change if INT is not outside window.
Even if BLM is changing, BLM will be clamped to max and min values per following code:
Code:
BLM clamp routine
;
;~~~~~~~~~~~~~~~~~~~~~
;
LEF2B LDAA L48F3 ;Upper limit for BLMs
LDAB L48F4 ;Lower limit for BLMs
;
LDX #L02D6 ;Addr of first BLM cell
LEF34 CMPA 0,X ;Compare upper lim. to BLM
BCC LEF3A ;Bra if BLM less
;
STAA 0,X ;Save upper limit instead
;
LEF3A CMPB 0,X ;Compare lower lim. to BLM
BLS LEF40 ;Bra if lower limit is less
;
STAB 0,X ;Save lower limit instead
;
LEF40 INX ;+1, advance to next cell
CPX #L02EA ;Last BLM cell
BLS LEF34 ;Bra if not at last cell yet, continue
;
RTS ;Return
This means that setting max and min BLM to 128 will cause ECM to check all 16 BLM cells to ensure they are between 128 and 128. If BLM in a cell is found to be outside the range then it is set to the limit instead, in this case 128.
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