DanBoris' Tech Blog - Game Control 2

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The reply to my last entry explaining the transistor portion of the game control circuit allowed me to work out the complete opertation of this section.

 

When the coin switch is activated it momentarily pulls /SRST low which resets the score counters. The two C9 inverters generating an active high reset signal which is also used to reset the score counters. When /SRST goes low it pulls the base of Q2 low which turns on Q2, which pulls the base of Q1 high turning Q1 on. With Q1 on the base of Q2 will be pulled low so even when the coin switch turns off Q2 and Q1 will stay on. At this point the game has been reset so /STOPG1 and /STOPG2 (Stop Game) are both high, setting pin 2 of D2 low. Pin 3 of D2 is being held low by Q1 so /ATRACT is high turning off the attract mode.

 

The game will stay in the state until one of two things happens.

 

1. If either score counter reaches the game ending score, /STOPG1 or /STOPG2 will go low, setting pin 3 of B2 high which will turn on the attract mode through D2. This will also put a low on pin 8 of E4 which turns off Q2 which turns off Q1.

 

2. If the Antenna input goes high as a result of a static shock to the machine, Q3 will turn on pulling the base of Q1 low, which turns off Q1 which turns off Q2.

 

After either of these situations has occurred Q2 and Q1 will be off, putting a high on pin 3 of D2 and keeping the game in attract mode. The game will stay in the state until the coin switch is activated again and the whole process starts over.

 

 

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