Chapter
5
Functional Description
5.1 Introduction
The Portable PLUS consis
ts
of the following circuits:
Motherboard
peA
(Assembly A2)
• Central processing unit (CPU) circuit.
• Peripheral processing unit (PPU) circuit.
• Address/control circuit.
• Keyboard interface.
• Liquid-crystal display (LCD) interface.
• HP-IL interface.
• Serial
(RS
-232-C) circuit.
• Video interface circuit.
• Modem interface circuit.
•
Clock/ready
circuit.
• Power supply.
Memory
peA
(Assembly A 1)
• System ROM
and
built-in
RAM
.
• Configuration EPROM.
• Plug-in ports.
Optional Modem
peA
(Assembly A3)
• Direct-connect modem.
The reference designation for each individual component contains a prefix
that
indicates its associated
PCA. For example, (A2Ul) indicates component
Ul
on assembly A2 (the motherboard PCA). Refer to
the schematic diagrams in chapter
12
for details
of
the components within each circuit.
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