diff --git a/src/mame/drivers/luckybal.cpp b/src/mame/drivers/luckybal.cpp
index 38386b42ce2..1349d3743b3 100644
--- a/src/mame/drivers/luckybal.cpp
+++ b/src/mame/drivers/luckybal.cpp
@@ -40,6 +40,45 @@
 
   Samples are 8-bit unsigned PCM.
 
+*********************************************************************
+
+  I/O:
+  
+  1x PPI 8255.
+  3x 4099 (8-Bit Addressable Latch).
+  3x 4512 (8-Channel Data Selector).
+
+      PPI 8255
+  .------v------.
+  |         PA0 |------> DAC (D7)
+  |         PA1 |------> DAC (D6)
+  |         PA2 |------> DAC (D5)
+  |         PA3 |------> DAC (D4)
+  |         PA4 |------> DAC (D3)
+  |         PA5 |------> DAC (D2)
+  |         PA6 |------> DAC (D1)
+  |         PA7 |------> DAC (D0)
+  |             |
+  |         PB0 |------> I/O 4099 (A0) & 4512 (A)
+  |         PB1 |------> I/O 4099 (A1) & 4512 (B)
+  |         PB2 |------> I/O 4099 (A2) & 4512 (C)
+  |         PB3 |------> I/O 4099 (WD 4099 #0, Players) 
+  |         PB4 |------> I/O 4099 (WD 4099 #1, Counters)
+  |         PB5 |------> I/O 4099 (WD 4099 #2, unknown)
+  |         PB6 |------> I/O 4099 (D)
+  |         PB7 |------> PB7
+  |             |
+  |         PC0 |------> EEPROM (DI)
+  |         PC1 |------> EEPROM (CS)
+  |         PC2 |------> EEPROM (SK)
+  |         PC3 |------\ tied together
+  |         PC4 |------/ to PC3.
+  |         PC5 |------> I/O 4512 #0 (SO, inputs #0)
+  |         PC6 |------> I/O 4512 #1 (SO, inputs #1)
+  |         PC7 |------> I/O 4512 #2 (SO, DIP switches)
+  '-------------'
+
+
 *********************************************************************/