HP 3000 SERIES II System Service Manual page 71

Maintenance Panel Operating Procedures
V BUS
SINGLE CYCLE
TIMERS
I
ERROR IINTRPT
lOP SINGLE STEP RESET
CLOCK
COMPARE
I REGISTER DISPLAY FREEZE
ENABLE
HALT
REGISTER ALT INHIBIT
ENABLE
INHIBIT ENABLE
EXT
INHIBIT
Q Q
~ ~
Q Q Q Q Q Q ~ ~ ~
Q Q
~
INHIBIT JUMP
HALT EXECUTE
U BUS
NORMAL ENABLE INHIBIT ENABLE INHIBIT EXECUTE
CPU I/O
INT
FREE SINGLE
EXIT '
JUMP RUN CYCLE
Table 3-1. Maintenance Panel Controls and Indicators (Continued)
PANEL
ROW PANEL MARKING
USE
11
ERROR FREEZE
In the ENABLE position, this switch causes a freeze when any of
(bistable switch) the following occurs:
•
Illegal memory address
•
Memory address parity error
•
MCUD parity error
•
System parity error
•
I/O data parity error
•
I/O address parity error
To end the freeze, the ERROR FREEZE switch is set to the down
position.
11 INTRPT (bistable When the computer is running, setting this switch to INHIBIT
switch) causes all internal and external interrupts to be ignored, with the
exception of the power failure interrupt. When the switch is
returned to the ENABLE position, the previously ignored interrupts
are processed. The switch performs no function when the com-
puter is halted.
11
lOP SINGLE STEP Enables or disables the lOP SINGLE STEP EXECUTE switch.
ENABLE/INHIBIT
(bistable switch)
11 lOP SINGLE STEP When enabled by the switch listed above, the lOP executes one
EXECUTE (spring-return step each time the switch is pressed.
switch)
11
RESET CPU (spring-
The CPU and MCU are reset when this switch is pressed. To avoid
return switch) improperly changing the contents of registers, the switch should
be pressed only when the computer is halted.
11
RESET I/O (spring- All I/O subsystems are reset when this switch is pressed.
return switch)
11
CLOCK EXT/INT
At the INT position, this switch allows the CPU to use the clock
(bistable switch)
pulse generated within the CPU. At the EXT position, the switch
selects a clock pulse produced by an external pulse generator.
The external clock-pulse must have the following characteristics:
•
Source impedance: 50 ohms or less.
•
Source must sink up to 60 mao
•
High level: +2.5V to 5.aV.
•
Low level: O.OV to OAV.
•
Maximum rise time: 10 nsec.
•
Maximum fall time: 10 nsec.
•
High time: 20 nsec to infinite time.
•
Low time: 20 nsec to infinite time.
•
Maximum frequency: 25.0 MHz.
•
Minimum frequency: 0 Hz.
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