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Skipping hex values is not so strange for a BCD counter (that would be invalid for a decoder IC); clarified the coincounter_w comment

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darq 2016-12-09 19:57:47 +01:00
parent 98ab24199d
commit 00f449c0ab
1 changed files with 8 additions and 5 deletions
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13
src/mame/drivers/shootout.cpp
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@ -76,12 +76,15 @@ WRITE8_MEMBER(shootout_state::flipscreen_w)
}
/*
This is actually a 'real' counter... the first write is always 0x40, then when a coin is inserted the game starts to count from 0x01,
then it counts from 0x02 to 0x09 but strangely it skips the 'hexadecimal letters'... so from 0x09 it goes to
0x10, 0x11, 0x12, ...0x19, 0x20, and so on...
The game counts up to 0x99, after that, 0x99 is always written...
This is actually a double BCD counter (2 BCD digits packet in a byte)...
The first write is always 0x40, then when a coin is inserted it starts to count from 0x01 up to 0x99.
When it reaches 99 credits, 0x99 is always written...
On the shootoutj and shootoutb sets, it works as above but it counts up to 0x09 instead of 0x99.
On the shootoutj and shootoutb sets, it works as above but it counts up to 0x09 instead of 0x99 (Single BCD digit).
Note:
This should be an input for a BCD to 7-segment decoder (e.g. a 74LS47), but all the PCBs I've seen don't have 'onboard'
display(s), so this was implemented as normal "coin counter" (after all, they both have the same goal: count credits ;))
*/
WRITE8_MEMBER(shootout_state::coincounter_w)
{