Physio Control LIFEPAK 9 - Page 43

VIDEO 1
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VIDEO 2 一 一 一 一
© August 1993 Physio-Control
Description 1
HALF-TONE NORMAL VIDEO FULL INTENSITY NORMAL VIDEO HALF-TONE
Figure 1-9 Video Intensity
Character dot information merges with trace information to create the video
input signal. Messages have priority over waveforms when the two types of
data are mapped to the same point on the CRT.
Video RAM. Trace and character data are stored in a 32k x 8 static RAM,
U21. New ECG data is stored during the horizontal retrace and consists of
twelve bytes. Horizontal retrace provides an interrupt to the
Display/Recorder microprocessor which signals permission for a memory
access. New data storage and memory address counter incrementing is
controlled by the Display/Recorder microprocessor.
An additional 512 bytes are used for storage of the character address codes
(similar to ASCII codes). The screen can be configured into a matrix of
16 x 32 character cells, with each cell accepting character information from
the Font EPROM. The message content is updated as needed by the
Display/Recorder microprocessor during horizontal retrace.
Font EPROM. A 32k x 8 EPROM, U22, contains character font patterns,
with memory for 256 characters. Each character is 16 pixels high and 24
pixels wide to fit in the screen character cells (see Figure 1-8). The
displayable character set includes single-sized numerals, punctuation, and
uppercase letters in normal, inverse, and boldface video. Special characters
and double-sized numerals are in normal video display.
Program EPROM. Another 32k x 8 EPROM, U14, contains the operating
software for the Display/Recorder microprocessor. Included in the software
is a list of codes representing all of the words and phrases used in the
annotated recorder text.
Program RAM. The Program RAM U13 is used by the Display/Recorder
microprocessor as a scratch-pad while performing program functions.
Additionally, all CODE SUMMARY data and the Display/Recorder
microprocessor bulletin board is stored in the Program RAM.
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