Emulex MD21/S2, Technical Manual

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User Panel Connection
Table 7-6. Connector J4 Pin Description
Pin Connection True Function
1 Ground
—
.
'
2 Power Fail Low
Detects DC Power Fail
3 SW3 High
Drive 2 Write Protect
4 LED 3 Low
Drive 2 Ready
5 SW2 High
Drive 1 Write Protect
6 LED 2 Low
Drive 1 Ready
7 LED 1 Low
Drive 2 Write Protect
8 None
—
Not Used
9 LED 0
Low
Drive 1 Write Protect
10 +5 volts
——
7.4.1 OUTPUTS FROM THE MD21
These output signals are driven by a 74LS374-type register. When a
low level is applied to any of these signal lines, the LED is lit
to indicate that the disk drive is either write-protected or on­
line.
7.4.2 WRITE-PROTECT INPUTS TO THE MD21
These inputs are pulled up with 4.7K ohms to +5 volts, and go to
74LS244-type receivers. When a low level is applied to any signal
line, the MD21 inhibits write operations to its respective drive.
Figure 7-7 illustrates the write-protect input signal.
+5
WRITE-PROTECT
SWITCH
Figure 7-7. Write-Protect Input Signal
Interfaces 7-19