HP 3000 SERIES II System Service Manual page 83

3-12. CPU REGISTER DISPLAYS
Maintenance Panel Operating Procedures
When CPU registers are displayed, the register contents are acquired either from the computer S bus or
R bus, dependingnon the bus to which the register is gated in the computer. In the case of the stack
registers, SP1, and the preadder, a switch on the Maintenance Panel permits display from either the S
bus or the R bus; this switch is titled SINGLE CYCLE REGISTER DISPLAY, ALT/NORMAL (panel row
11).
3-13. GENERAL-USE DISPLAY
When the REGISTER SELECTION TEST lamp is lighted, any 16 bits or 16 binary signals can be applied
for display to jack J3 of the MPI PCA (figure 3-4). The bits or signals must have TTL silicon logic levels.
They are displayed in the REGISTER DISPLAY (0:15) lamps on the Maintenance Panel. The pins in J3
to which connection is made are listed in table 3-2. The table also shows two trigger pulses and a
+
5 volt
source; these are supplied by the MPI PCA. The MR signal is an input to the PCA, used for factory test
purposes.
For any particular application of the general-use display, a cardboard overlay can be made for the
REGISTER DISPLAY lamps, with appropriate signal names marked on the overlay. (A ticket punch is a
suitable device for making the holes in the cardboard.)
3-14. MAINTENANCE PANEL TEST
The following test checks the operability of most circuits in the Maintenance Panel. Most circuits in the
MPI PCA are not checked. If performed as described, and if step
a
below has previously been completed,
the test can be executed without interfering with normal computer functioning. (Switch information from
the Maintenance Panel does not enter the computer system when switch S1 on the MPI PCA is at the
SWITCH TEST position.)
3-15. LAMP TEST
To exercise the lamp test function, perform the following steps:
a. Connect the Maintenance Panel to the computer system in the normal manner (figure 3-4). Before
making connection, be sure
+
5 volts has been removed from the system, and make sure all bistable
switches on the Maintenance Panel are down.
b. At the MPI peA, set switch S1 to the LAMP TEST position. Every lamp on the Maintenance Panel
should light.
c. Set S1 to the SWITCH TEST position. Some lamps should go out.
CAUTION
Before performing step d below, be sure S1 has been set to the
SWITCH TEST position, otherwise switch information may enter the
computer system. The switch information is the result of voltage
spikes produced when the plug is removed from Jl.
d. Remove the plug from receptacle Jl on the Maintenance Panel. All lamps should go out. Replace the
plug.
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