SCSI Card port SCSI System Cable
DB-25 connector Apple 50 pin connector
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Pin Signal Pin
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1 REQ' Request 49
2 MSG' Message 46
3 I/O' 50
4 RST' Reset 45
5 ACK' Acknowledge 44
6 BSY' Busy 43
7 GND Ground 16,18,19
8 DB0' Data Line 0 26
9 GND Ground 20,21,22
10 DB3' Data Line 3 29
11 DB5' Data Line 5 31
12 DB6' Data Line 6 32
13 DB7' Data Line 7 33
14 GND Ground 1,2,3
15 C/D' Carrier Detect 48
16 GND Ground 4,5,6
17 ATN' Attention 41
18 GND Ground 7,8,9
18 DIFFSENS-GND 11
19 SEL' Select 47
20 DBP' Parity 34
21 DB1' Data Line 1 27
22 DB2' Data Line 2 28
23 DB4' Data Line 4 30
24 GND Ground 23,24,25
25 TERMPWR 38
Important SCSI Card Information
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The prime (') next to the signal name indicates the signal voltage levels are negative, "low true". The SCSI port uses -5V logic levels.
Because the SCSI port is a DB-25 connector, it looks like a RS-232 port but is NOT a RS-232 port. DO NOT plug any RS-232 device into the SCSI port. Doing so can damage the 5380 chip on the card.
Article Change History:
15 Nov 1996 - Reviewed for technical accuracy, revised formatting.