Traced through the inputs for optispark. Both wind up in unidentified logic but the signal conditioning part is complete. This is a work in progress but will shuffle to the back burner for a bit.

While doing this, I have identified another chip if this is of interest. Parts marked
014
P66AB
83833

are a quad Nand or And function. I need to sort out which (easy once I get the scope on it). I believe the part to be 74HC08 or possibly 74HC00. This part is used in the bank switching for the 28F010 Flash. In that application, A15 is one input and Port A bit 5 is used to switch the upper half of the FLASH. In this way the lower 32K of the address space remains constant while only the upper 32 is switched.

OK so back to opti... here is the info on the input signal conditioning. Interesting to note, going back to spfautsch's reply that the Hi Res signal is inverted in the signal conditioning comparitor. Hmmmm

-Tom

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HiRes_RB_SS.jpg

High Resolution signal enters through connector:
Connector C2 (BLACK)
Pin 20
Wire Purple/White
Circuit 430
Name High Resolution Signal

1 Capacitor to ground HIRES_C1
2 1K Pull up resistor to +5V HIRES_R1
3 100K resistor to Node A HIRES_R2
4 Capacitor to ground HIRES_C2
5 Resistors HIRES_R3 AND HIRES_R4 form a divider between 5V and ground
this 2.5 volt reference is the +VE input to comparitor 2 on pin 11
6 Resistor HIRES_R5 connects to the -VE Input of comparitor pin 10
7 LM339 is an open collector type ouput on pin 13. HIRES_R6 is used to
pull the output to +5V.
8 HIRES_R7 provides feedback/hysteresis to the +VE input / voltage divider.
9 Pin 4 of the unknown 28 pin PLCC see below


Comparitor chip is marked
014
M66DB
89551

Believed to be a LM339 quad comparitor or a variant
that shares the pin configuration.

Unknown 28 pin PLCC
609-3700521
CP08978
144436
9638N
SYMBIOS LOGIC
726


LoRes_RB_SS.jpg

Low Resolution signal enters through connector:
Connector C2 (BLACK)
Pin 2
Wire Red/Black
Circuit 453
Name Low Resolution Signal

1 Capacitor to ground LORES_C1
2 1.0K Pull up resistor to +5V LORES_R1
3 100K resistor to Node A LORES_R2
4 Capacitor to ground
5 10K Resistor to Node B LORES_R3
6 Resistor feedback LORES_R4
7 +VE Input of comparitor LM339 pin 9
8 -VE Input of comparitor pin 8 to pins 4,6 and 10
these inputs are biased to 2.5V by components
Resistor VATS_R5
Resistor VATS_R6
Capacitor VATS_C3
9 LM339 is an open collector type ouput. LORES_R5
resistor pulls the output to +5V. Output is pin 14
10 Unknown logic chip pin 9


Comparitor chip is marked
014
M66DB
89551

Believed to be a LM339 quad comparitor or a variant
that shares the pin configuration.

Unknown logic chip is TI branded and marked
014
P63SN
73098