Connector - Apple Macintosh Portable ROM Expansion50 PIN UNKNOWN CONNECTOR| Pin | Name | Description |
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| 1 | +5V | +5 VDC | | 2 | A1 | Address bit 1 | | 3 | A2 | Address bit 2 | | 4 | A3 | Address bit 3 | | 5 | A4 | Address bit 4 | | 6 | A5 | Address bit 5 | | 7 | A6 | Address bit 6 | | 8 | A7 | Address bit 7 | | 9 | A8 | Address bit 8 | | 10 | A9 | Address bit 9 | | 11 | A10 | Address bit 10 | | 12 | A11 | Address bit 11 | | 13 | A12 | Address bit 12 | | 14 | A13 | Address bit 13 | | 15 | A14 | Address bit 14 | | 16 | A15 | Address bit 15 | | 17 | A16 | Address bit 16 | | 18 | A17 | Address bit 17 | | 19 | A18 | Address bit 18 | | 20 | A19 | Address bit 19 | | 21 | A20 | Address bit 20 | | 22 | A21 | Address bit 21 | | 23 | A22 | Address bit 22 | | 24 | A23 | Address bit 23 | | 25 | GND | Ground | | 26 | GND | Ground | | 27 | /DTACK | Data Transfer Acknowledge | | 28 | /AS | Address Strobe | | 29 | /ROM_CS | ROM Chip Select | | 30 | 16M | 16 MHz Clock | | 31 | /EXT_DTACK | External Data Transfer Acknowledge | | 32 | /DELAY_CS | | | 33 | D0 | Data bit 0 | | 34 | D1 | Data bit 1 | | 35 | D2 | Data bit 2 | | 36 | D3 | Data bit 3 | | 37 | D4 | Data bit 4 | | 38 | D5 | Data bit 5 | | 39 | D6 | Data bit 6 | | 40 | D7 | Data bit 7 | | 41 | D8 | Data bit 8 | | 42 | D9 | Data bit 9 | | 43 | D10 | Data bit 10 | | 44 | D11 | Data bit 11 | | 45 | D12 | Data bit 12 | | 46 | D13 | Data bit 13 | | 47 | D14 | Data bit 14 | | 48 | D15 | Data bit 15 | | 49 | +5V | +5 VDC | | 50 | +5V | +5 VDC |
D0-D15Unbuffered data bus, bits 0 through 15 A1-A23Unbuffered 68HC000 address bus, bits 1 through 23 16M16 MHz system clock /EXT.DTACKExternal data transfer acknowledge that disables main system /DTACK. /AS68HC000 Address strobe /DTACKData transfer acknowledge, /DTACK input to 68HC000. /DELAY_CSThis signal is generated by the addressing PAL and is used to put the ROM board into the idle mode by inserting multiple wait states. /ROM_CSPermanent ROM chip select signal. Selects in range $90 0000 through $9F FFFF.
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