HP 3000 SERIES II System Service Manual page 72

System Service
V BUS
SINGLE CYCLE
TIMERS I ERROR IINTRPT
lOP SINGLE STEP RESET
CLOCK
COMPARE
I
REGISTER DISPLAY FREEZE
ENABLE HALT REGISTER ALT INHIBlf 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 1/0 INT FREE SINGLE
EXIT JUMP RUN
CYCLE
REGISTER SELECTION
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
SP3
MOD
CMO
I/O
1i0
SP2 OPNO CPXl CPX2 SR NO. ION
OEV NO. 100 lOP DATA MAP PCLK TEST R RGTR S RGTR
8 8 8 8 8 8
8 8 8 8 8 8 8 8 8 8 8 8
MEM
MEM
AORS
DATA
STATUS PB
PL
OL RC CNTR CIR
0 0 0 0 0 0 0 0 0 0
0 0
0 0 0
0 0 0
Table 3-1. Maintenance Panel Controls and Indicators (Continued)
PANEL
ROW
11
11
12
PANEL MARKING
CLOCK INHIBIT/FREE
RUN (bistable
switch)
CLOCK SINGLE
CYCLE (spring-return
switch)
REGISTER SELECTION
fl"'rY"'lne- "'nrl I"'e>nte>r ",ff
\ I U l l l f ' J v U I I U \.J"-'lll\..l1 V I I
spring-return switches)
USE
To equal the internal clock-pulse rate, the external clock-pulse
frequency must be 22.8571 MHz. This corresponds to a period of
43.75 nsec, which, because of a divide-by-four action in the CPU,
provides a 175-nsec computer clock cycle.
The external clock-pulse is supplied to a BNC-type connector on
the CPU backplane. The connector is labelled EXT - CLOCK. A
50-ohm termination impedance is provided in the CPU.
In the INHIBIT position, this switch permits the CPU to execute one
machine cycle each time the CLOCK SINGLE CYCLE switch is
pressed. In the FREE RUN position of the switch, the CPU
operates continuously using either internal or external clock
pulses.
When enabled by the CLOCK INHIBIT/FREE RUN switch, pressing
this switch causes execution of one CPU machine cycle.
When pressed up or down, each switch lights the lamp above or
he>I""'f it "'nrl tllrne- ",ff ",n\f ",the>r li,."hte>rl 1"'rY"'ln in the> ,."r"" In Thn
U\....fIVVV I l , U I I U l U I I I . v V I I LAIIJ V l l l \..11
1I~lll'-'U
I U l l l t J I I I til"",,
~IVUt-'.
III\.;'
lighted lamp identifies the register displayed by the REGISTER
DISPLAY lamps. The B14 and B15 lamps remain extinguished
except as stated below.
The lighted REGISTER SELECTION lamp also identifies the
register which will be loaded by either of the LOAD REGISTER
switches.
The following registers cannot be loaded by the LOAD REGISTER
FROM SW RGTR switch; these are identified below as
"display only" registers.
3-10