Printer; Real-Time Clock - HP Integral Personal Computer Service Manual

1-14 FunctiOlUll Deaorlptlon
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Computer
5.12 Printer
The Integral PC includes an 80-column dot matrix inkjet printer that uses a disposable printhead. (The
printer is a modified ThinkJet HP-IL printer.) Figure 5-5 is the printer block diagram.
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HEAD DOTI
MOTOR CONTROL
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PRINT!JII
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OUT -OF ·P"'PEA
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LOGIC A PCA
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Laale • PCA
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- - - CCIITROL CIRCUITS
p .. ..,. 1-1. Printer Block
Dla.ram
The printer uses an HP-IL interface (U31 on the logic B
peA)
to communicate with the computer.
It
has a custom-designed controller IC (U28 on the logic B PCA), a lK-byte RAM
Ie
(U27 on the logic B
PCA), and a 16K-byte ROM IC (U32 on the logic B PCA).· The lK-byte RAM IC buffers at least one
line of 12 by 640 dot graphics. The 16K-byte ROM
Ie
contains the character font table.
The control panel includes a form-feed key, a line-feed key, and a continue-operation key that is used
to set the top-of-form position and to recover from errors. The panel includes an attention light (the
yellow LED) that comes on continuously to indicate an out-of-paper condition and blinks to indicate
an error condition.
The printer provides printing and non -printing self tests to identify failures.
5.13 Real· Time Clock
The real-time dock (located on the logic B PCA) keeps time continuously, even while the computer
is
turned off. The clock also provides the timing for the operating system.
• The printer ROM Ie is localized for some languages. Currently the standard version
is
used for all languages except Arabic, Hebrew,
and Japanese.