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fix incomplete info (n/w)

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Lord-Nightmare 2016-09-26 01:29:09 -04:00
parent 85410f9a24
commit 2639397a9c
1 changed files with 7 additions and 4 deletions
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11
src/mame/drivers/superqix.cpp
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@ -68,10 +68,13 @@ Super Qix:
The V1.1, V1.2 and US PCBS have two resistors from VCC to GND forming a
voltage divider on top of 7H, the resistor from VCC/Pin 14 to Common is
22KOhms, the other resistor is unknown and seems to connect to GND/Pin 7.
The center of the two resistors connects to one end of a 0.1uf capacitor,
the other end of the capacitor connects to 7H pin 12.
This implies some sort of brief/reset pulse generation or filter on pin 12.
22KOhms, the other resistor is also 22KOhms and seems to connect to
GND/Pin 7. The center of the two resistors connects to one end of a 0.1uf
capacitor and also to 7H pin 4, the other end of the capacitor connects to
7H pin 12.
This implies some sort of brief/reset pulse generation or filter on pin 12,
or more likely some abuse of the TTL input hysteresis of the 74LS86 IC itself
such that transitions of pin 12 cause transitions on pin 4 as well, or similar.
Again, what exactly this accomplishes is unclear without further tracing.
- sqixb2 is a bootleg of sqixb1, with the MCU removed.