Physio Control LIFEPAK 9 - Page 40

LIFEPAK 9 defibrillator/monitor
when they are required for a particular function. This data is transmitted in
packets containing a header byte, two ECG sample bytes, and, if required, a
data/command byte.
The first four VO lines listed in Table 1-4 communicate with the Display
Gate Array, U29, driving the input for the Display PCB. The other five YO
lines control the operation of the recorder.
Table 1-4 Display/Recorder Microprocessor VO Lines
VO Line Signal Direction
P(50) H.RETR In
P(52) GO Out
P(53) |INCMEM Out
P(54) |TR/CHAR Out
P(21) STROBE Out
P(60) RECORDER POWER Out
P(61) PRINTHEAD CURRENT SENSE In
P(66) PRINTHEAD TYPE In
P(67) PRINTHEAD LOAD Out
System Clock. Crystal-controlled multiple-output oscillator U10 provides a >
16MHz square wave to the Display Gate Array. It also supplies 8MHz to
both the System and Display/Recorder microprocessors (U30 and U1), and
2MHz to A/D converter U9 on the Power Conversion PCB.
Address Decode. Programmable logic array U9 controls the reading from
and the writing to all external memory and the Recorder Gate Array, U3. U9
functions as an address decoder and is programmed to enable the appropriate
devices when the Display/Recorder microprocessor addresses different areas
in memory.
Buffers U11, U12, and U1S5 isolate the appropriate RAM/ROM memory
devices from interaction with the Display/Recorder microprocessor. U11
buffers the data bus. Buffers U12 and U15 control interaction on the address
bus between the Display/Recorder microprocessor, the Display Gate Array,
and the RAM/ROM memory devices.
Display Gate Array. Display Gate Array U29 is a custom IC containing
many blocks of standard OR and AND gate circuits (counters, multivibrators,
flip-flops, etc.). A metalized layer added on top of the gate circuits connects
only those circuits needed for a specific function: Monitor PCB sync timing,
ECG memory addressing, ECG display trace generation, video intensity, and
additional timing signal generation. Two different internal counters control
1-26 All Rights Reserved O August 1993 Physio-Control