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Input/Output Ports

Port Number (hex) Input Function Output Function
0 COL0R Color Register 0 (Right)
1 COL1R Color Register 1
2 COL2R Color Register 2
3 COL3R Color Register 3
4 COL0L Color Register 0 (Left)
5 COL1L Color Register 1
6 COL2L Color Register 2
7 COL3L Color Register 3
8 CONCM Consumer/Commercial mode (i.e., low- or high-resolution) INTST Intercept Status Feedback (collision detection)
9 HORCB Horizontal Color Boundary, BG Color
A VERBL Vertical Blank Register
B COLBX Color Block Transfer
C MAGIC Magic Register
D INFBK Interrupt Feedback
E INMOD Interrupt Enable and Mode VERAF Vertical Address Feedback (light pen)
F INLIN Interrupt Line HORAF Horizontal Address Feedback (light pen)
10 TONMO Tone Master Oscillator SW0 Player 1 Control Handle
11 TONEA Tone A Frequency SW1 Player 2 Control Handle
12 TONEB Tone B Frequency SW2 Player 3 Control Handle
13 TONEC Tone C Frequency SW3 Player 4 Control Handle
14 VIBRA Vibrato/Tremolo KEY0 Keypad Column 0 (right)
15 VOLAB Tone C Volume, Noise Modulation Control KEY1 Keypad Column 1
16 VOLC Tone A Volume, Tone B Volume KEY2 Keypad Column 2
17 VOLN Noise Volume KEY3 Keypad Column 3 (left)
18 SNDBX Sound Block Transfer
19 XPAND Expander Pixel Definition
1C POT0 Player 0 Pot
1D POT1 Player 1 Pot
1E POT2 Player 2 Pot
1F POT3 Player 3 Pot

Port Descriptions

CONCM ($8)

Select video mode (0 = low res 160×102, 1 = high res 320×204).

VERBL ($A)

Vertical Blank. The Address chip needs this register to determine the scan line below which Screen Refresh is no longer needed. The Data chip must duplicate this register to determine when to turn on the border color.

INMOD ($E)

Interrupt Enable and Mode/Vertical Line Feedback. On write, this register enables interrupts and determines the interrupt mode of each. On read, this register contains the vertical line number that a Light Pen Interrupt was received on. Bit 3 of the Interrupt Enable port (0x0E) when set enables line interrupts, while bit 1 of the same register enables the Light Pen interrupt.

INLIN ($F)

Interrupt Line/Horizontal Address Feedback. On write, this register sets the scan line number on which to generate a line interrupt back to the Z80. On read, this register contains the horizontal address (i.e., position in the line) that a Light Pen Interrupt was received on.

[NM:106, 143, source listing 5] Reference: Wizard of Wor arcade disassembly