31 lines
1.0 KiB
Plaintext
31 lines
1.0 KiB
Plaintext
Macintosh SE VIA pin assignments.
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VIA Data register A:
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7 Input vSCCWrReq 0 = SCC Wait/Request, channel A or B
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6 Output vPage2 0 = alternate screen buffer, 1 = main screen buffer
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5 Output vHeadSel Floppy disk state-control line SEL
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4 Output vDriveSel 0 = upper internal floppy disk drive, 1 = lower
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3 Output vSync 1 = synchronous model support, channel A
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2 Output vSound(2) Sound volume
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1 Output vSound(1) { (111 = maximum, 000 = minimum;
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0 Output vSound(0) bit 2 = most significant bit )
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VIA Data register B:
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7 Output vSndEnb 0 = sound enabled
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6 Output vH4 0 = SCSI IRQ enabled
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5 Output vFDesk2 ADB state input 1 (ST1)
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4 Output vFDesk1 ADB state input 0 (ST0)
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3 Input vFDBInt 0 = ADB interrupt
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2 Output rTCEnb 0 = real-time clock enabled
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1 Output rtcCLK Real-time clock's serial data-clock line
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0 In or Out rtcData Real-time clock's serial data line
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VIA Peripheral Control register:
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CB2 7-5 Apple Desktop Bus data
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CB1 4 Apple Desktop Bus clock
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CA2 3-1 One-second interrupt
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CA1 0 Vertical blanking interrupt
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