Apple PowerBook 520 Technical Information Page 43

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CHAPTER 3
I/O Features
SCSI Port 29
SCSI Connectors 3
The internal and external HDI-30 connectors are identical to those used in other
PowerBook models. The SCSI portion of the Combo IC connects directly to the internal
and external SCSI connectors and can sink up to 48 mA through each of the pins
connected to the SCSI bus. The data and control signals on the SCSI bus are active low
signals that are driven by open drain outputs.
Table 3-11 shows the signal assignments for the internal and external SCSI connectors.
Note that pin 1 of the external HDI-30 connector is the /SCSI.DISK.MODE signal.
Table 3-11 Internal and external HDI-30 SCSI connector signals
Pin
number
HDI-30
(internal)
HDI-30
(external)
1 DISK.+5 /SCSI.DISK.MODE
2 DISK.+5 /DB0
3 GND GND
4 GND /DB1
5 GND TERMPWR (not used;
reserved for future use)
6 /DB0 /DB2
7 /DB1 /DB3
8 /DB2 GND
9 /DB3 /ACK
10 /DB4 GND
11 /DB5 /DB4
12 /DB6 GND
13 /DB7 GND
14 /DBP /DB5
15 DISK.+5 GND
16 /BSY /DB6
17 /ATN GND
18 /ACK /DB7
19 GND /DBP
20 /MSG GND
21 /RST /REQ
22 /SEL GND
continued
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