HP 8112A Operating, Programming And Servicing Manual page 271

Servicing the Microprocessor and Front-panel
Theory of Operation
Introduction
The microprocessor board is the control center of the HP 81 12A.
The microprocessor monitors the keyboard and HP-IB , interprets the
key-presses and commands, and implements them by sending control
data to the control circuits and updating the front-panel display and
LEDs.
When in remote control mode all the front panel keys, except
are ignored by the microprocessor. If the local lockout command has
been received on the HP-IB then the
O a t a Bu s
D i s p l a y Bo a r d
Figure 1 o.7-1. Microprocessor board architecture
Figure 10.7- 1 summarises the parts of the microprocessor board and
the connecting busses. The purpose of the address bus is to allow the
microprocessor to select a particular location in the instrument. The
location can be in ROM , in RAM , in the GPIA, or one of the other
devices. The data bus allows the microprocessor to read data from,
C o n t r o l
Servicing the Microprocessor and Front-panel 1 0.7-1
1 0 . 7
key is also ignored.
K e y b o a r d
Keyboard
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Bo a r d