Fluke ScopeMeter 123 Service Manual page 53

ROM control for PCB versions < 8
The Flash ROM mode depends on the output signal of the RESET ROM circuit, RP#:
•
RP#>2V, software can run. True if +12V present and/or ROMRST is high.
•
RP#<2V, software cannot run. True if +12V not present and/or ROMRST is low
(test tool off).
•
RP#>12V, software can run, and ROM can be programmed. True if +12V is present.
The +12VPROG voltage is derived from the power adapter input voltage by the P-ASIC
on the POWER part. To program the ROM, the power adapter voltage must be
+20V±1V, to ensure a correct +12V voltage level.
ROM control for PCB versions 8 and newer
FlashROMs used on PCB version 8 and newer do not need the 12V programming
voltage.
The circuit D480 and related parts create a delay for the ROMWRITE enable signal.
This prevents the ROM write proces being disabled before all data have been written.
RAM
Measurement data and instrument settings are stored in RAM D475. All RAM data will
be lost if all power sources (battery and power adapter) are removed.
mask ROM
The D-ASIC has on-chip mask ROM. If no valid Flash ROM software is present when
the test tool is turned on, the mask ROM software will become activate. The test tool
can be forced to stay in the mask ROM software by pressing the ^ and > key, and then
turning the test tool on. When active, the mask ROM software generates a 100 kHz
square wave on pin 59 of the D-ASIC.
Display Control
The LCD unit includes the LCD, the LCD drivers, and the fluorescent back light lamp.
It is connected to the main board via connector X453. The LCD is built up of 240
columns of 240 pixels each (240x240 matrix). The D-ASIC supplies the data and
control signals for the LCD drivers on the LCD unit (Figure 3-13).
Circuit Descriptions
3.3 Detailed Circuit Descriptions
3
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