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
Содержание MD21/S2
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