Circuit Descriptions
5–10
1502C MTDR Service Manual
combinations of A
12
and A
11
and operate on A
10
, A
9
, and A
8
to generate the enable,
select, and trigger signals CS00 through CS31. These occupy the remaining address
space, locations EOOOH to FFFFH.
An automatic wait state is inserted for all circuits selected by U2022. The wait state
is used by the processor to compensate for the slow access times of U2041, U2046,
and U4020 on the Main Board; U2023 on the Front Panel Board; and U2040 on the
display module. The wait request is generated by U1041.
The select signals from U2024 are also modified through U1043B by a 200-ns pulse.
This pulse is created from gates U1042B, U1031C, U2040C, and J-K flip-flop
U2033A. This circuit creates a write pulse that ends prior to the completion of the
processor bus cycle, thus meeting data hold time requirements for some selected
ICs.
The most significant address bit on the EPROM is set or reset by bank-switching
flip-flop U2023A. Another control signal, heat disable, is generated by a similar
flip-flop, U2023B. This is also toggled by two select lines.
The interrupt logic consists of an eight-bit tri-state buffer, U1032, and gates U1030
and U1031D. Six interrupt requests signals are logically OR’d by U1030, then
inverted by U1031D and applied to the microprocessor interrupt request input. Five
of the interrupts are received from the video ADC, the digital timebase, a real-time
counter, the front panel control ADC, and from the Option Port connector. The sixth
interrupt input is unused.
The six interrupt requests and two power status signals are connected to pull-up
resistors R1033 and the inputs of buffer U1032. When the microprocessor responds
to an interrupt request, it selects U1032, allowing the eight inputs to that device to
be placed on the data bus for reading.
The processor system outputs six control signals to the Driver/Sampler module.
These signals are loaded from the data bus into latch U3010 by a select signal from
the address decoder. These signals are used by the 1502C Driver/Sampler and the
Option 06 adapter (if equipped).
Option Port Interface
The option port interface consists of the following:
H
Supply Controller
H
Buffers
H
Output Latch
The option port interface provides the connection between the processor system and
external options. This port has a unique protocol that must be followed for proper
Additional Decoding
Interrupt Logic
Introduction
Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
To Next Page
Loading...
Need help?
General
