HP PageWriter XL M1705B Service Manual page 10

5. Theory of Operation
Operational Overview .............. 5-1
ECG Data Path ............... 5-1
Power-on and Power-off Sequences .......
5-2
Power-on ................. 5-2
Power-off ................. 5-2
Circuit Descriptions .............. 5-4
The Standard Patient Module
..........
5-6
CPU Assembly .................
5-8
CPU .................... 5-8
System Memory ............... 5-10
ROM .................... 5-10
I/O Control .................
5-12
The FGA ................. 5-12
Serial Communications ........... 5-14
Digital Signal Processor ............
5-14
System Expansion Connector
.........
5-15
Disk Drive (M1700A and M1701A only) ..... 5-15
Power Supply ................. 5-16
VMAIN and VIN ...............
5-16
Battery Charger and Battery Sensor ...... 5-18
Battery Operation and Condition ....... 5-18
5 Volt Regulator ............... 5-19
+5 Overvoltage/Undervoltage Sensor ...... 5-19
Printer Switch ................
5-20
Battery Switch ................ 5-20
ACON Detector ...............
5-20
+5 Backup Supply and Low Battery Disconnect . .
5-21
+5 to Backup Switchover ...........
5-21
Patient Module Voltage Regulator
....... 5-21
The Keyboard and Keyboard Display .......
5-22
Printer ....................
5-22
Printer Gate Array .............. 5-22
Printer RAM ................
5-22
Motor Driver ................
5-22
ADC (Analog-to-Digital
Converter) ....... 5-23
Thermal Printhead .............. 5-23
The Preview Display ..............
5-24
Preview Logic Board .............
5-25
Preview Display Power Supply Board ...... 5-26
VLCD Supply ...............
5-27
VCFL Supply ...............
5-27
Preview Screen ................
5-27
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